Caramelized Onion & Thyme Tartlets

Buttery, flaky tart shells filled with rich, sweet caramelized onions and accented with the subtle aroma of fresh thyme – these Caramelized Onion & Thyme Tartlets offer a refined and deeply savory flavor profile. Perfect for entertaining, holiday spreads, or elegant starters, they bring out the best in simple, wholesome ingredients with gourmet appeal.

Why You’ll Love This Recipe

These tartlets are a beautiful marriage of rustic and refined. The slow-cooked onions develop a deep sweetness, complemented by the tang of balsamic vinegar and the earthy brightness of fresh thyme. Wrapped in a crisp, golden pastry shell, they make a wonderful appetizer that’s both comforting and sophisticated. They are also highly adaptable, can be made ahead, and are easy to transport – ideal for gatherings.

ingredients

(Tip: You can find the complete list of ingredients and their measurements in the recipe card below.)

• puff pastry or shortcrust pastry

• olive oil

• yellow onions, thinly sliced

• balsamic vinegar

• brown sugar

• salt and pepper to taste

• fresh thyme leaves (plus extra for garnish)

• egg (for egg wash)

directions

1. Preheat oven to 375°F (190°C). Lightly grease a muffin tin or tartlet pans.

2. Roll out the pastry and cut into circles to fit your tartlet molds. Press the pastry into the molds and prick the bottoms with a fork. Chill in the fridge for 10 minutes.

3. In a large skillet, heat olive oil over medium-low heat. Add the sliced onions and cook slowly, stirring frequently, for 25–30 minutes until soft and golden.

4. Stir in the balsamic vinegar, brown sugar, thyme, salt, and pepper. Cook for an additional 2–3 minutes, then remove from heat.

5. Spoon the caramelized onion mixture into the chilled pastry shells.

6. Brush the edges of the pastry with beaten egg for a golden finish.

7. Bake for 18–22 minutes or until the pastry is crisp and golden.

8. Garnish with additional thyme leaves before serving.

9. Serve warm or at room temperature.

Servings and timing

Servings: 12 tartlets
Preparation time: 20 minutes
Cooking time: 30 minutes (plus 20 minutes baking)
Total time: 1 hour 10 minutes

Variations

• Add goat cheese or brie to the base of each tartlet before adding the onions for added creaminess.

• Use red onions for a sweeter, deeper flavor and richer color.

• Incorporate roasted garlic for a deeper savory depth.

• Top with a sprinkle of parmesan before baking for a nutty crust.

• Add a pinch of chili flakes for a subtle heat.

storage/reheating

Store leftover tartlets in an airtight container in the refrigerator for up to 3 days. Reheat in a 325°F (160°C) oven for 10–12 minutes to restore crispness. Avoid microwaving as it may make the pastry soggy. Tartlets can also be frozen and reheated directly from frozen in the oven.

FAQs

Can I make these tartlets ahead of time?

Yes, they can be assembled a few hours in advance or baked and reheated just before serving.

Can I use store-bought caramelized onions?

While fresh caramelized onions provide the best flavor, store-bought can be used in a time crunch.

What’s the best pastry to use?

Puff pastry offers a light, flaky texture while shortcrust gives a more buttery, structured bite.

Can I make these vegan?

Yes, use a plant-based pastry and omit the egg wash or replace it with plant milk.

Can I serve them cold?

They’re best served warm or at room temperature, but they’re still flavorful when chilled.

Do I need to blind-bake the pastry?

No blind-baking is required since the filling is not overly wet, and chilling the pastry prevents sogginess.

Can I use dried thyme?

Fresh thyme is recommended, but you can use half the amount of dried thyme in a pinch.

Can I use a mini tart pan instead of a muffin tin?

Yes, any tartlet mold or mini tart pan will work well.

How can I ensure even caramelization?

Cook onions over low heat, stir frequently, and be patient — caramelizing takes time.

Can I scale this recipe for a large tart?

Yes, the same filling can be used in a full-sized tart shell; increase baking time to 30–35 minutes.

Conclusion

Caramelized Onion & Thyme Tartlets are a standout appetizer that showcases how a few simple ingredients, when treated with care, can create something truly elegant. Whether you’re hosting a cocktail party, planning a holiday spread, or preparing a sophisticated starter, these tartlets offer warmth, flavor, and visual appeal in every bite.