The Recipe Index A small-batch recipe journal

Recipe · By Erin Clarke (Well Plated)

Upside-Down French Onion Tart

savourytartonionpuff pastryappetizer
Ingredients
10
Method
7 steps
Collected
2026-10-29
A rectangular puff-pastry tart with browned red-onion rounds, thyme and visible melted cheese on a dark wooden board.
Original source

01

Ingredients

  • 2 small to medium red onions
  • 2 tbsp extra-virgin olive oil
  • 4 tbsp honey or hot honey
  • ½ tsp flaky sea salt, plus extra to finish
  • ½ tsp ground black pepper
  • 6–8 sprigs fresh thyme, plus extra leaves to finish
  • 3 oz (about 85 g) Gruyère, thinly sliced
  • 1 sheet frozen puff pastry, thawed according to its package
  • 1 large egg beaten with 1 tsp water, for brushing
  • Balsamic glaze, optional, to finish

02

Method

  1. Heat the oven to 400°F (about 205°C; the creator does not specify an oven mode). Line a rimmed baking sheet with baking parchment.
  2. Peel the onions and cut crosswise into roughly ¼-inch (6 mm) rings, keeping the layers of each ring together.
  3. Make six evenly spaced patches of olive oil on the parchment, arranged in two rows of three. Drizzle the honey over them, season with the measured salt and pepper, and put a small thyme sprig on each patch.
  4. Place a large onion ring over each patch and fill the spaces between them with smaller rings, making a fairly close-packed rectangle.
  5. Arrange the Gruyère over the onions, leaving a border of at least 1 inch (2.5 cm). Roll out the puff pastry into a rectangle larger than the onion layer, drape it over the filling, and press the edges with a fork. Brush lightly with the egg-and-water wash.
  6. Bake on the middle rack for 25–30 minutes, until the pastry is puffed and deeply golden. Rest for 5–10 minutes.
  7. Put a large board over the tray and carefully invert both together; peel away the parchment. Add balsamic glaze if using, fresh thyme and a little flaky salt. Slice into squares and serve.

03

Sources & attribution

  • Erin Clarke (Well Plated), “Upside Down French Onion Tart” — YouTube Short, video, transcript and description checked 2026-10-29.
  • Erin Clarke, “Onion Tart” on Well Plated, written ingredients, method, yield and storage notes checked 2026-10-29.
  • Illustration: locally AI-generated for this collection, selected by the collection owner; not an original Well Plated photograph.