Ingredients
For the Crust:
- 200 g all-purpose flour 1⅜ cup + 2 tbsp
- 113 g cold butter diced (1 stick)
- 80 ml ice water ⅓ cup
- 5 g fine sea salt ¾ tsp
- 6 g sugar ½ tbsp
For the Filling:
- 3 medium tomatoes sliced ¼ inch thick
- 1 red onion sliced thin
- 2 tbsp olive oil
- 1-2 heaped tablespoons Dijon mustard
- ½ tsp fine sea salt for tomatoes
- 1 tsp fresh or dried herbs thyme, oregano, basil
- ½ tsp black pepper
- 1 cup Gruyère or cheese of choice shredded
- Parmesan grated (to taste)
- 1 egg beaten (for egg wash)
For Finishing (Optional but Beautiful):
- Mascarpone
- Balsamic glaze
- Fresh basil leaves
Method
- Make the crust by food processor (easiest): Pulse flour, salt, and sugar together in food processor. Add cold diced butter and pulse 8-10 times until mixture resembles coarse breadcrumbs with pea-sized pieces. Add ice water while pulsing just until dough comes together (don't overwork). Gather into a disk, wrap in plastic, and chill for at least 1 hour (can be made ahead up to 3 days).
- OR make the crust by hand: Combine flour and salt in a bowl. Add sugar if using. Add cold butter and rub into flour with a pastry blender or your fingertips until it resembles coarse breadcrumbs with pea-sized pieces of butter throughout. Sprinkle ice water gradually over mixture, tossing gently with a fork until dough just comes together in a shaggy mass. Don't overmix. Gather into a disk, wrap in plastic, and chill for at least 1 hour (can be made ahead up to 3 days).
- Prepare the filling: While dough chills, place sliced tomatoes in a colander and sprinkle with ½ tsp salt. Let drain for 30 minutes to remove excess moisture. Toss red onion with olive oil, herbs, and black pepper in a bowl. Set aside.
- Assemble: Lightly flour a sheet of parchment paper. Roll chilled dough directly on the parchment into a 12" circle. Transfer the parchment with dough to a baking sheet. Spread Dijon mustard over the dough, leaving a 2" border around the edges. Layer cheese over the mustard. Pat dry the drained tomatoes and toss with the onion mixture. Arrange tomatoes in overlapping rows over the cheese. Scatter the rest of the seasoned onions over the tomatoes. Sprinkle generously with Parmesan. Fold the edges of dough up and over the filling, creating a rustic border. Brush exposed dough edges with beaten egg.
- Bake: At 400°F for around 45 minutes (check at the 35 minute mark), until crust is deep golden brown and cheese is melted and bubbly at the edges. Tomatoes should look slightly caramelized.
- Finish (Optional but Beautiful): Once baked and still warm, dollop or drizzle mascarpone over the galette. Drizzle with balsamic glaze. Top with a few fresh basil leaves. Enjoy!
