In a food processor, add flour, salt and cubed butter. Pulse until you get a crumbly texture where the butter is about the side of a pea.
With the processor running, stream in ice cold water slowly until your dough forms a ball.
Remove the dough ball from the processor and form into a disk about 1" (2cm) thick. Cover with plastic wrap and refrigerate for 30 minutes.
Prepare your ingredients
While your dough is resting in the fridge, cut your heirloom tomatoes into ¼" (0.5cm) slices. Place sliced tomatoes on paper towel to absorb excess liquid. This will help make sure we don't end up with a soggy galette. Allow your tomatoes to drain on the paper towel for at least 20 minutes.
Take your herbed cream cheese out of the fridge and allow it to come to room temperature.
Assemble your galette
Preheat your oven to 400F (200c).
Roll out your galette dough between two pieces of parchment paper using a rolling pin. The goal is to end up with a circle that is about 15" (38cm) and about ⅛" (.25cm) thick. This doesn't have to be exact. Rustic is fine!
Once your galette dough is rolled out, remove the top layer of parchment and transfer the dough with the lower piece of parchment to a baking sheet.
Spread the herbed cream cheese evenly on your dough, leaving about 1" (2cm) around the border uncovered.
Arrange your tomato slices as you wish and season your tomatoes with salt and pepper. Add thyme sprigs on top of tomatoes.
Carefully crimp or fold the edge of the galette dough over itself to create a nice border that will hold in the ingredients as they bake.
Brush the crimped crust with egg yolk and sprinkle with za'atar spice.
Bake and Garnish
Bake for 25-30 minutes. Keep an eye on the oven. Since every oven is different you may need to adjust the temperature or time.
Once finished baking, remove from oven and allow to the galette to cool for 15 minutes. Garnish with fresh basil leaves and good extra virgin olive oil.
Notes
This recipe can be adapted with different herbs. Store any uneaten slices in the fridge for up to 2 days.