Use a fork or pastry cutter to cut the butter into the flour. Stop when the mixture resembles course crumbs.
Mix in water one tablespoon at a time, adding just enough for dough to clump together (typically 3 to 4 tablespoons total).
Shape dough into a flat circle about 1-inch thick. Wrap in plastic wrap, then chill for at least 1 hour.
Prepare Filling:
Preheat oven to 400°F (200°C).
Stack 4 large sheets of paper towel together.
Core tomatoes, then slice ¼-inch thick. Place tomatoes in a single layer on paper towels.
Sprinkle tomatoes with salt and pepper, then set aside for at least 15 minutes.
In a small bowl, mix together cream cheese, pesto, and lemon zest. Season to taste with salt and pepper.
Assemble Galette:
On a lightly floured surface, use a rolling pin to roll pastry into a 12-inch circle. Transfer to a parchment paper-lined baking sheet.
Spread cream cheese filling over pastry, leave a 1 ½-inch border.
Use a dry paper towel to blot tomatoes, removing more liquid. Then arrange tomatoes over cream cheese filling, layering as needed to fit.
Fold pastry edge over tomatoes, overlapping where needed.
Whisk together egg and 1 tablespoon water. Brush egg wash over pastry.
Bake galette until dough is deep gold brown and crisp, and tomatoes are tender (about 40 to 45 minutes).
Let galette rest for 10 minutes, then cut into wedges and serve. Enjoy!
Notes
I used 3 large tomatoes (or 1 pound 6.7 ounces / 645 grams). You can make this recipe work with slightly different amounts of tomatoes though, so don't worry if you're a little short.If you have one, I recommend using a food processor to make the pastry crust. It's less messy and comes together faster.This recipe only uses the zest from the lemon. Save the juice for another recipe, or use it to make this Lemon Olive Oil Dressing or this Single Serving Lemonade.Make sure to read the info before this recipe card for helpful tips, step by step photos, variations, serving suggestions, and more!