Caramelized Onion Jam Crostini – Sweet, Savory & Perfect for Parties

If you love appetizers that feel fancy but are surprisingly simple to make, these caramelized onion jam crostini will become your new favorite. The slow-cooked onions turn irresistibly sweet, rich, and flavorful, and when paired with crisp toasted bread, it creates a bite-sized treat everyone loves. I first made this recipe for a small family gathering, and it disappeared within minutes—people kept asking, “What is this?!” Since then, it has become my go-to appetizer for holidays, dinners, and potlucks.
This easy homemade caramelized onion jam crostini recipe is perfect when you want something elegant without spending hours in the kitchen.

Ingredients

For the Caramelized Onion Jam

4 large yellow onions, thinly sliced
3 tablespoons olive oil
2 tablespoons butter
3 tablespoons brown sugar
1 teaspoon salt
½ teaspoon black pepper
3 tablespoons balsamic vinegar
¼ cup water

For the Crostini

1 French baguette, sliced into ½-inch pieces
3 tablespoons olive oil (for brushing)
1 cup soft cheese such as cream cheese or goat cheese
Fresh thyme or parsley for garnish (optional)

Step-by-Step Instructions

Make the Caramelized Onion Jam

Heat a large pan over medium heat and add 3 tbsp olive oil and 2 tbsp butter.
Add the 4 sliced onions, salt, and black pepper. Cook for 10 minutes, stirring often until the onions begin to soften.
Sprinkle in 3 tbsp brown sugar and continue cooking for 20–25 minutes until the onions are deep golden and sticky.
Add 3 tbsp balsamic vinegar and ¼ cup water, then cook another 5–7 minutes until the mixture becomes jam-like.
Remove from heat and let it cool slightly.

Prepare the Crostini

Preheat your oven to 190°C (375°F).
Arrange the baguette slices on a baking tray and brush each piece with a little olive oil.
Bake for 8–10 minutes or until lightly golden and crisp.
Let the crostini cool, then spread each piece with a small layer of cream cheese or goat cheese.
Top with a spoonful of the caramelized onion jam and finish with a sprinkle of thyme or parsley if desired.

Tips & Variations

Add a savory twist: Stir in a pinch of smoked paprika or chili flakes to the onion jam for a deeper flavor.
Change the cheese: Instead of cream cheese, try ricotta, feta, burrata, or a mild melting cheese.
Add texture: A sprinkle of crushed walnuts or toasted almonds adds a delicious crunch.

Storing & Reheating

Store leftover onion jam in an airtight container in the refrigerator for up to 5 days.
It also freezes very well—keep it in a freezer-safe jar or bag for up to 2 months.
Reheat gently in a pan over low heat with a splash of water to bring back its smooth, jammy consistency.
The crostini are best assembled fresh, but you can toast the bread ahead of time and store it in an airtight container for 24 hours.

FAQs

Can I make this recipe ahead?

Yes! You can prepare the onion jam 1–2 days ahead and store it in the fridge. Assemble the crostini just before serving.

Can I use gluten-free bread?

Absolutely. Simply choose a gluten-free baguette or crackers.

Can I make the onions without sugar?

Yes, but they will take longer to caramelize and won’t be as jam-like. You can reduce the sugar or replace it with a natural alternative like honey.

What cheese works best?

Creamy, mild cheeses pair wonderfully with sweet onions. Goat cheese, cream cheese, ricotta, or even brie work beautifully.

Nutritional Information

Approximate per 1 crostini (varies by bread size and cheese amount):

Calories: ~105
Protein: ~2 g
Carbohydrates: ~12 g
Fat: ~5 g

These caramelized onion jam crostini are a simple yet impressive appetizer perfect for dinner parties, family gatherings, or cozy nights when you want something special. If you try this recipe, leave a comment below and let me know how it turned out!
Feel free to share this post on social media and check out my other easy homemade appetizer recipes for more delicious ideas.