In a food processor, combine all-purpose flour, Parmesan cheese, Italian seasoning, black pepper, sugar, and salt. Pulse until well blended.

Add very cold unsalted butter in chunks, pulsing until the mixture resembles coarse crumbs.

Gradually add ice water, pulsing until the dough just comes together. Avoid overworking.

Wrap the dough tightly in plastic wrap and refrigerate for at least one hour.

Heat olive oil in a skillet over medium heat. Sauté the chopped onion until translucent, for about 5-7 minutes.

Add minced garlic and cook for an additional minute until fragrant. Remove skillet from heat.

Preheat your oven to 400°F (200°C). Roll out the chilled dough into a 12-inch circle on parchment.

Spread the onion and garlic mixture in the center, leaving a 2-inch border.

Layer with white cheddar cheese, fresh herbs, and sliced tomatoes. Season with salt and pepper.

Fold the dough edges inward creating a rustic edge for the galette.

Brush the edges with heavy cream and bake for 35-45 minutes until golden brown.

Let cool for 10 minutes before slicing. Serve warm or at room temperature.