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Slow-cooking the onions brings out their natural sugars, for a deep, intensely flavorful topping that’s high in nutrients and low in fat and calories. You can customize by adding chopped arugula, roasted tomatoes, or wild mushrooms. Or swap gluten-free, Paleo, or Keto bread for the baguette.
- In large, heavy skillet, heat olive oil over medium heat. Add onion and toss to coat with oil. Cook 20–25 minutes, stirring frequently until onions are golden-brown and soft. Stir in rosemary and cook 2 minutes longer.
- Remove from heat and let cool. Stir in olives and season to taste with salt and pepper. Transfer to tightly sealed container and refrigerate until ready to serve.
- While onions are cooking, preheat oven to 400°F. Line baking sheet with parchment paper. Arrange baguette slices on baking sheet. Brush tops with olive oil and bake 7–10 minutes, until golden and crispy. Remove from heat and sprinkle with salt. Let cool and store in tightly sealed container until ready to serve.
- To serve, top each baguette slice with caramelized onion and olive mixture. Arrange on serving platter, garnish with fresh rosemary, if desired, and serve immediately.
If you’re looking for more make-ahead holiday appetizers, you may like these, too:
- Serving Size 2 crostini
- Calories 300
- Carbohydrate Content 54 g
- Cholesterol Content 0 mg
- Fat Content 5 g
- Fiber Content 0 g
- Protein Content 10 g
- Saturated Fat Content 0.5 g
- Sodium Content 540 mg
- Sugar Content 3 g