Caramelized Onion and Egg Tartine Recipe

Caramelized Onion and Egg Tartine

Makes 2

Caramelized onions mingle beautifully with melty cheese and sliced egg in this tartine. Think of it as an open-faced grilled cheese sandwich with all the flavors of French Onion Soup – perfect for breakfast or lunch!


  • 4 tablespoons unsalted butter, divided use
  • 1 yellow onion, thinly sliced
  • Kosher salt, to taste
  • Pepper, to taste
  • 2 slices crusty bread
  • 1/2 cup Gruyère cheese, grated
  • 2 large eggs, hard-boiled, and sliced
  • 4 sprigs thyme, leaves picked
  • Marmite (See Cook’s Tip)
  • Aged balsamic vinegar
  • Flaky sea salt


  1. Melt 2 tablespoons butter in a large, oven-safe skillet over medium heat. Add onions. Cover with a lid and cook until onions are translucent, about 4 minutes. Remove lid, mix well, and increase heat to medium-high.
  2. Continue to cook, stirring often, until onions have caramelized to a deep golden brown, about 6 to 8 minutes. Any burnt-on bits can be dissolved and incorporated by adding 1 - 2 tablespoons water. Once caramelized, season with salt and pepper, to taste. Transfer onions to a plate. Set aside and wipe out pan.
  3. Melt another tablespoon butter in pan. Add bread slices, pushing them around to coat the bottoms with butter. Toast on medium heat, 2 to 3 minutes until golden. Add final tablespoon of butter. Flip bread slices and push around to coat second side.
  4. Turn oven broiler on high and set rack one notch below the top shelf.
  5. Spread a thin layer of marmite on each piece of toast, if using. Pile caramelized onions on top, followed by grated cheese. Place skillet under broiler, 2 to 3 minutes until cheese has melted.
  6. Remove from oven. Nestle a sliced egg into the melty cheese. Top with thyme leaves. Garnish with a drizzle of aged balsamic and a sprinkle of flakey sea salt, if using.
  7. Cook’s Tip:
  8. Marmite is a British, plant-based, spreadable condiment made from yeast extract. It is deeply savory and salty, with surprisingly beefy notes. USE SPARINGLY. A little goes a long way. A very thin layer spread on the toasted bread will put this dish over the top!


Amount Per Serving (based on 2 servings)
Calories: 510 undefined
Fat: 38 g
Saturated Fat: 21 g
Trans Fat: 1 g
Cholesterol: 275 mg
Sodium: 410 mg
Carbohydrates: 23 g
Fiber: 2 g
Sugar: 5 g
Added Sugars: 1 g
Protein: 18 g
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