To roast tomatoes, onions & garlic:

Preheat oven to 375 degrees F.  Cover a sheet tray with aluminum foil for easy cleanup, set aside.

In a small, microwave-safe bowl, add onions and water. Cover with wax or plastic wrap, vent with a small slash, and microwave on high for four minutes. Drain.

Place tomatoes on one side of the sheet pan, the onions on the other, and drizzle the onions with the red wine vinegar. Drizzle both the onions and tomatoes with two to three tablespoons olive oil then sprinkle with salt. Add the garlic packet.

Roast in the oven until the cut edges & bottoms of the tomatoes begin to pick up a little light color, 1 1/4 to 1 1/2 hours, removing and turning from time to time and stirring the onions now and then. Pay closer attention after about 35 minutes; you will need to stir the onions more after that point. If you’ve used any smaller or cherry tomatoes, they will need to be removed sooner than the rest.

Remove the tray from the oven and give a final stir to the onions and loosen any tomatoes that may be sticking to the foil. Set aside to cool. When cool enough to handle, open the garlic packet, squeeze out the garlic into a small bowl and roughly mash. Drain the juices off of the tomatoes. Do not turn off oven. When ready to proceed with the galette, increase the oven temperature to 400 degrees F.

For the Galette:

Dust a large sheet of parchment paper lightly with flour. Roll out the pastry crust into a 15-inch circle. (See note.) This is a rustic galette, so the edges don’t have to be perfect. Piece back together as needed.

Sprinkle the center of the pie crust with bread crumbs, keeping about two inches of the outside edge clear. Layer on the onions in the center of the crust, leaving about two inches around the outside edge. Dot with the garlic, and place the tomatoes on top, cut side up. Scatter the goat cheese over the tomatoes, sprinkle with 1/2 teaspoon of thyme.

Lift the outside edge of the crust, using the parchment paper to help lift, if needed, and fold over the galette. Lift another section and pleating in two-inch sections, work around the crust in the same manner.

Transfer, parchment and all, to a cookie sheet. Brush the edges with the egg yolk/water mix, being careful not to let the mixture seep heavily where the crust meets the parchment. Sprinkle the whole galette, including the edge with sea salt.

Bake the galette until the filling is bubbling hot in the center and the pastry is golden brown, 30 to 35 minutes. Let cool at least 10 minutes on the baking sheet.

Lift parchment and galette onto a serving platter. Use a thin spatula to very slightly lift the galette and slide off of the parchment if desired. Sprinkle with remaining thyme. Serve the galette hot, warm or at room temperature. Pass the red wine vinegar to sprinkle on top, if desired.

Note: If using a homemade crust, the galette can be made a bit larger. See the body of post.