Red Onion Tart

Ingredients (16)

• + 1 (.25 ounce) package active dry yeast add to pantry
• + 1 pinch white sugar add to pantry
• + ½ cup warm water add to pantry
• + 1 egg, at room temperature add to pantry
• ✓ 3 tablespoons butter, at room temperature
• ✓ 2 ½ cups all-purpose flour
• + 1 teaspoon salt add to pantry
• + 2 teaspoons lemon zest add to pantry
• + ½ teaspoon vegetable oil add to pantry
• + ½ red onion, sliced add to pantry
• + 1 cup shredded Gouda cheese add to pantry
• + ½ cup grated Parmesan cheese add to pantry
• + 2 jarred roasted piquillo peppers, diced add to pantry
• ✓ ¼ teaspoon ground black pepper to taste
• + 1 ½ cups heavy cream add to pantry
• + ¼ teaspoon stone-ground mustard add to pantry