Tomato & Plum Galette with Black Pepper-Parmesan Crust

Name: Tomato & Plum Galette with Black Pepper-Parmesan Crust
Cuisine: French
Ingredients: 1 1/4 cup unbleached all-purpose flour; 2 tablespoon finely grated Parmesan; 1/2 teaspoon freshly ground black pepper; 1/2 teaspoon sea salt; 8 tablespoon (1 stick) unsalted butter, cold; 2 tablespoon sour cream, cold; 5 tablespoon ice water, plus more as needed; 3 cup small heirloom tomatoes (I used a mix of cherry, grape, and plum varieties); 1 dash sea salt; 3 medium black plums; 1/4 cup finely grated Parmesan, divided; 1 egg, lightly beaten; 1 dash ground black pepper; 1 tablespoon torn tarragon leaves