Caramelized Onion and Spinach Crostini
on Dec 29, 2019, Updated May 07, 2025
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The thyme and lemon zest bring this fairly earthy spinach-onion topping to life in this beautiful and simple crostini recipe.
I go through crostini and bruschetta phases. One season, pretty much every appetizer I serve is perched on a little piece of toast, then I move on for a while, and then — hey! I get to rediscover this highly pleasurable way of serving and eating all kinds of things.
Crostini are the smaller one- or two-bite-sized versions of these topped grilled or toasted bread recipes, and perfect for appetizers with cocktails. This vegetarian take is so simple — easy to make, with only a few ingredients and the straightforward flavors of the vegetables really shine.
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Ingredients
It never ceases to amaze me how so much raw spinach cooks down to so little. You’ll probably want to add the spinach in a few batches, adding more as each batch wilts down. Keep folding the spinach into the caramelized onions as you add the greens.
You can use roughly chopped mature spinach instead of baby spinach; just make sure to cut out any tough stems. You can also use other greens like chard or kale, but you may need to cook them a bit longer to get them tender, especially if the leaves are thicker/more mature. This mixture would make an excellent side dish as well.
The thyme and lemon zest bring this fairly earthy spinach-onion topping to life. A final sprinkle of the zest at the end makes them absolutely stunning.
More Great Crostini & Bruschetta Recipes
- Avocado and Cannellini Bean Crostini with Gremolata
- Prosciutto, Asian Pear, and Blue Cheese Crostini
- Salmon and White Bean Bruschetta
- Tomato Bruschetta
Also Read: What’s the Difference Between Bruschetta and Crostini?
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Caramelized Onion and Spinach Crostini
Ingredients
- 1 baguette (sliced into 1/3-inch thick slices)
- 5 tablespoons olive oil (divided; or more as needed)
- kosher salt
- 2 Vidalia or other sweet onions (halved and thinly sliced)
- Freshly ground black pepper (to taste)
- 8 ounces baby spinach
- 1 teaspoon minced fresh thyme
- Zest of 1 lemon (plus more for garnish)
Instructions
- Preheat the oven to 350 F.
- Place baguette slices on a baking sheet. Brush them with about 3 tablespoons worth of olive oil, and lightly sprinkle them with salt. Bake for about 4 minutes, until barely golden around the edges, but not hard — they will firm up as they cool. Let them cool to room temperature.
- Meanwhile, heat the remaining 2 tablespoons of olive oil in a large skillet over medium heat. Add the onions and cook, stirring occasionally, for about 20 minutes until they are very soft and nicely browned. Add a bit of water periodically towards the end if they start to stick to the pan. Season with salt and pepper. Add the spinach and a couple of tablespoons of water and sauté for another 4 minutes or so until the spinach is wilted, the water is evaporated and everything is well combined. Stir in the thyme and lemon zest. Taste and adjust the seasoning as needed.
- Spoon the mixture onto the toasts. Serve pretty quickly so they don’t get soggy.
