In a large mixing bowl, whisk to combine the flour, sugar, salt, and pepper. Fold in the cheese. Add the butter and smash it into the flour until you have a shaggy mixture. Drizzle in 1/3 cup of water and fold until the dough holds together.

Turn the dough out and form it into a rough disc. Wrap in plastic wrap and chill in the fridge for 30 minutes.

On a floured surface, roll the dough out into a 3/4-inch rectangle. Fold into quarters, re-wrap, and chill for 30 minutes. Repeat this process 2 to 3 more times.

Prep the zucchini by layering them on a cutting board with towels, sprinkling lightly with sea salt, and covering with more towels. Set aside for at least 30 minutes.

Preheat oven to 425 degrees F. Line a 13 x 18-inch baking sheet with parchment paper.

Roll the dough out into a 15 x 20-inch rectangle and set it in the prepared baking sheet. Chill until ready to assemble.

In a small skillet over medium heat, add oil, shallots, and red pepper flakes. Cook for about 3 minutes until shallots are toasted. Mix with Dijon mustard in a small bowl.

Spread the shallot-Dijon mixture over the tart dough, leaving a 2-inch border. Sprinkle with all but 2 tablespoons of cheese. Layer zucchini slices, overlapping them, and finish with black pepper. Brush dough border with egg wash, fold, and crimp corners closed, then brush with more egg wash.

Bake for 20 minutes, then sprinkle remaining cheese and bake for an additional 10-15 minutes until zucchini edges are golden and crust is deep golden brown.

Set tart aside to cool for 10 minutes, sprinkle with basil, slice, and serve.