Torta Pasqualina

Ingredients

• ["3 1/2 cups all-purpose flour", "2 Tbsp. sugar", "1 1/2 tsp. kosher salt", "1 1/2 cups (3 sticks) unsalted butter, cut into pieces, chilled in freezer", "3 1/2 lb. Swiss chard (about 5 bunches), ribs and stems removed", "3 Tbsp. extra-virgin olive oil", "2 medium onions, finely chopped", "10 large eggs", "1 1/2 cups whole-milk fresh ricotta, preferably box-drained, patted dry", "4 oz. Parmesan, coarsely grated", "1 large garlic clove, finely grated", "2 tsp. finely grated lemon zest", "1/4 tsp. freshly grated nutmeg", "2 tsp. kosher salt, plus more", "1 1/2 tsp. freshly ground black pepper, plus more", "All-purpose flour (for surface)", "2 tsp. sugar", "A 10\"-diameter tart pan with a removable bottom""]"