Low-carb, keto-friendly vegetarian dinner of pan-roasted balsamic Brussels sprouts and caramelized red onions, finished with two soft-boiled or runny eggs. The caramelized vegetables deliver a rich umami flavor that makes this a comforting, nutritious meal.
If you want an easy, low-fuss dinner, roasted or pan-seared vegetables topped with a runny egg are a perfect go-to. This dish follows that idea: caramelized red onions and balsamic-seared Brussels sprouts finished with soft-boiled, poached, or over-easy eggs. If you have baby spinach on hand, wilt a handful under the eggs for extra greens.
Why you’ll love this recipe
- Simple ingredients and straightforward technique—only a handful of items needed (not counting salt, pepper, and olive oil).
- A satisfying vegetarian main thanks to the protein from eggs.
- Brussels sprouts are packed with vitamins and fiber, making this dish both healthy and filling.
Main ingredients & notes
See the recipe card below for exact measurements and full directions.
- Red onion — thinly sliced for caramelizing.
- Brussels sprouts — trimmed and halved for even searing.
- Garlic — fresh cloves or garlic paste work well.
- Balsamic vinegar — a fruity balsamic adds brightness; citrus-infused variants are great if available.
- Melty cheese (optional) — a mild melting cheese such as Monterey Jack or fontina can be added at the end.
- Eggs — poached, soft-boiled, or fried over-easy; use the type you prefer.
- Celery salt — a final sprinkle of celery salt brightens the dish and adds an unexpected savory note.
Disclosure: This post may contain affiliate links to products and foods used in the kitchen. At no additional cost to you, purchases made through those links may earn a small commission.
Recommended equipment
- Medium or large skillet (a cast-iron skillet gives excellent sear)
- Sharp chef’s knife
- Tongs for turning sprouts and onions
- Spatula
- Small pot if you plan to poach or soft-boil eggs
Instructions overview
Full, detailed instructions are in the recipe card below. Here’s a quick summary of the main steps.
Step 1 — Caramelize the onions
Cook thinly sliced red onions in a tablespoon of olive oil with a pinch of salt over medium heat. Once they begin to soften and color, reduce the heat to medium-low and continue cooking for 10–15 minutes until they reach your preferred level of caramelization. Remove them from the pan and set aside.
Step 2 — Sear the Brussels sprouts
In the same skillet, add the remaining olive oil and the halved Brussels sprouts, flat side down. Season with salt and pepper. Cook undisturbed over medium heat so the flat sides brown and develop a good sear, about 5–8 minutes depending on size. Add balsamic vinegar and toss to coat.
Step 3 — Finish
Return the caramelized onions to the pan and continue cooking until the Brussels sprouts are tender, about 8–12 minutes more. Finish with celery salt, kosher salt, and black pepper to taste. Top each serving with a runny egg—poached, soft-boiled, or fried over-easy.
Shopping, prepping & cooking tips
Onions
If you’re sensitive to onions while slicing, chilling them in the freezer for 10 minutes helps reduce eye irritation. For even slices, cut the onion in half lengthwise, remove the root stub, and slice lengthwise so the slices lay flatter in the pan.
Brussels sprouts
When possible, buy Brussels sprouts still attached to the stalk for maximum freshness. To prep, trim the tough bottom nub, peel away any discolored outer leaves, and halve each sprout lengthwise so the flat surface gets a good sear.
Tips to simplify and save time
- Toss the halved sprouts in olive oil and balsamic and air-fry them while you caramelize the onions in a skillet. When the sprouts are crisp and browned, combine them with the onions and finish with seasonings.
For meat eaters at the table
For a non-vegetarian option, fry a few slices of bacon cut into lardons in the skillet before cooking the onions. Remove the bacon, caramelize the onions in the bacon fat, then return the bacon at the end for added richness.
Balsamic Roasted Brussels Sprouts & Onions with Runny Eggs
Low-carb, keto-friendly vegetarian dinner of balsamic roasted Brussels sprouts and caramelized onions topped with runny eggs. Caramelization adds deep savory flavor.
Ingredients
- 2 cups thinly sliced red onions (about 1 large)
- 2 tablespoons extra virgin olive oil, divided
- 1 teaspoon kosher salt, divided
- 1/4 teaspoon black pepper, divided
- 1 pound Brussels sprouts, trimmed and halved
- 1 tablespoon balsamic vinegar
- 1/4 teaspoon celery salt, or to taste
- 4 large eggs
Instructions
- Thinly slice the red onion and halve the Brussels sprouts after trimming bottoms and removing any damaged leaves.
- Warm 1 tablespoon olive oil in a skillet over medium-high heat. Add the sliced onions with 1/4 teaspoon salt and 1/8 teaspoon black pepper. Cook, tossing occasionally, until they begin to soften, then lower heat to medium-low and cook 10–15 minutes until caramelized to your liking. Remove onions to a bowl.
- Add the remaining tablespoon of olive oil to the skillet and arrange Brussels sprouts flat-side down. Season with remaining salt and pepper. Cook undisturbed over medium heat until the flat sides are well-seared, about 5–8 minutes. Check after 5 minutes to monitor browning.
- Add the balsamic vinegar and toss to coat the sprouts. If the pan looks dry, add a drizzle more olive oil. Return the onions to the pan and cook another 8–12 minutes, until sprouts are tender. Season with celery salt, kosher salt, and black pepper to taste.
- While the sprouts finish, prepare the eggs: poach, fry over-easy, or soft-boil (8–10 minutes for soft-boiled, then cool and peel under running water). Serve sprouts and onions topped with the runny eggs.
Notes
Onions: Chilling onions briefly before slicing can reduce tearing. Slice lengthwise so pieces lay flat and caramelize evenly.
Brussels sprouts: Buying them on the stalk improves freshness. Halving them exposes more surface for delicious browning.
Nutrition (per serving, approximate)
Calories: 218 | Carbs: 19 g | Protein: 11 g | Fat: 12 g | Fiber: 5.7 g
