🔪 Step-by-Step Instructions: How to Make Caramelized Red Onion Tart with Feta

Step 1: Caramelize the Red Onions

1. Set a 12-inch non-stick skillet over low to medium-low heat.
2. Add 2 tablespoons olive oil (or butter). Once shimmering, add sliced red onions.
3. Stir gently to coat. Cook uncovered, stirring every 3–5 minutes.
4. After 10 minutes, sprinkle in 1 tsp sugar to help enhance sweetness and speed up caramelization.
5. Continue to cook for 25–30 minutes, stirring occasionally. Onions should soften, shrink in volume, and become golden and jammy.
6. If they brown too fast or start sticking, reduce the heat and add 1–2 tbsp water to deglaze.
7. Once deeply caramelized, stir in 2 tsp balsamic vinegar. Cook 2–3 more minutes to absorb.
8. Season with salt and pepper. Remove from heat and let cool for at least 5 minutes before using.

Pro Tip: Low and slow wins the flavor race. Patience gives the onions their melt-in-your-mouth sweetness.

Step 2: Prepare the Puff Pastry

1. Preheat oven to 400°F (200°C) with a rack in the center. Line a rimmed baking sheet (approx. 9x13 inches) with parchment paper.
2. On a lightly floured surface, roll out the puff pastry to smooth any creases (roughly 10x12 inches).
3. Transfer to the prepared baking sheet.
4. Using a paring knife, score a 1-inch border around the edge of the pastry — don’t cut through! This creates a raised crust when baking.

Step 3: Assemble the Tart

1. Spoon the caramelized onions evenly within the scored border.
2. Crumble feta cheese over the onions.
3. Scatter sliced black olives evenly on top.
4. Sprinkle with fresh thyme leaves.
5. Add chili flakes or honey drizzle if using.

Step 4: Egg Wash and Bake

1. Beat the egg in a small bowl and brush only the outer border with egg wash to encourage golden puffing.
2. Bake for 20–25 minutes, until the pastry is puffed, crisp, and golden, and feta has light browning spots.

Step 5: Cool, Slice, and Serve

1. Remove tart from oven. Let it cool on the baking sheet for 5–10 minutes to allow the crust to firm up.
2. Slice into squares or rustic wedges.
3. Serve warm, or let cool to room temperature before serving on a board or platter.

Serving Temperature: Best enjoyed warm or at room temp