Prepare the Crust
In a bowl, mix flour and salt.
Cut in cold vegan butter using a pastry cutter or fork until mixture resembles coarse crumbs.
Add ice water one tablespoon at a time, mixing gently until dough forms.
Shape into a disk, wrap, and chill for 30 minutes.
Prep the Filling
Slice tomatoes and pat dry with paper towels to remove excess moisture.
Toss lightly with olive oil, salt, pepper, and thyme.
Roll the Dough
Preheat oven to 400°F (200°C).
Roll chilled dough into a 12-inch circle on parchment paper.
Transfer parchment with dough onto a baking sheet.
Assemble the Galette
Spread Dijon mustard or vegan pesto in the center, leaving a 2-inch border.
Arrange tomato slices evenly over the spread.
Sprinkle with fresh basil.
Fold edges of dough over tomatoes, pleating as needed.
Optional: Brush crust lightly with olive oil for golden color.
Bake
Bake for 30–35 minutes, until crust is golden brown and tomatoes are softened and slightly caramelized.
Let cool for 10 minutes before slicing.