Slice tomatoes and spread them on paper towels. Sprinkle with 1/2 tsp salt and let sit for 15–20 minutes to draw out moisture. Pat dry gently.

In a bowl, combine flour and salt. Cut in cold butter using a pastry cutter or fingers until the mix resembles coarse crumbs. Add ice water 1 tbsp at a time until dough holds together. Form into a disk, wrap, and chill for 20 minutes.

Preheat to 400°F (200°C). Line a baking sheet with parchment paper.

Roll chilled dough into a 12-inch circle. Transfer to baking sheet. Spread Dijon mustard over the center, leaving a 2-inch border. Crumble goat cheese over mustard. Layer tomato slices over cheese, overlapping slightly. Season with pepper and a bit more salt. Fold edges of crust up over filling, pleating as needed. Brush crust with egg wash.

Bake for 35–40 minutes, until crust is golden brown and tomatoes are soft and juicy.

Let cool for 5–10 minutes. Sprinkle with torn fresh basil and serve warm or room temp.