Preheat your oven to 500°F (260°C). If using a pizza stone, place it on the middle rack while preheating. If using a baking sheet, lightly oil it or line with parchment. Lightly dust a work surface with the all-purpose flour.

Shape dough

On the floured surface, stretch or roll the prepared pizza dough into a roughly 12-inch round (or desired size). Transfer dough to a lightly-floured pizza peel or the prepared baking sheet. Brush a 1/2-inch rim of the dough lightly with 1 tablespoon olive oil to encourage browning.

Sauce

Make garlic-lemon olive oil

Warm 1 tablespoon extra-virgin olive oil in a small skillet over low heat for 30 seconds. Add the minced garlic and gently warm until fragrant but not browned, about 30–45 seconds. Remove from heat, stir in 1 teaspoon lemon juice, 1 teaspoon salt and 1/2 teaspoon black pepper. Allow to cool slightly.

Apply sauce

Brush the garlic-lemon oil evenly over the stretched dough, leaving the oiled rim intact. This acts as a light base in place of tomato sauce, imparting bright garlic-lemon flavor that complements the spinach and feta.

Cheeses & toppings

Wilt the spinach

Heat a large skillet over medium-high heat and add 1 teaspoon olive oil (from the finishing amount is fine). Add the 6 cups fresh spinach in batches if needed, tossing until just wilted, about 2–3 minutes. Remove from heat and, while still warm, transfer to a colander and press gently with the back of a spoon to remove excess moisture. Pat the spinach dry with paper towels; excess water will make the pizza soggy.

Season spinach

Place the drained spinach in a bowl and toss with the lemon zest and 1/4 teaspoon crushed red pepper flakes (reserve the remainder for the pizza or to taste). Adjust salt lightly — feta is salty, so start with a small pinch.

Assemble cheeses and toppings

Spread dollops of the ricotta (1/2 cup) in even spoonfuls across the oiled dough, leaving space between them. Sprinkle the shredded mozzarella (1 cup) evenly over the surface, focusing slightly toward the center. Distribute the wilted and dried spinach in an even layer over the cheeses. Scatter the crumbled feta (8 oz) across the pizza, and add the thinly sliced red onion (1/4 cup) evenly on top. Finish with a light sprinkle of the remaining crushed red pepper flakes if desired.

Baking & finishing

Bake

Slide the pizza onto the preheated stone or place the baking sheet in the oven. Bake at 500°F (260°C) for 8–12 minutes, rotating once halfway through for even browning, until the crust is golden and the cheese is melted and bubbling (browning of the feta is optional). Oven times vary—watch closely.

Finish and serve

Remove the pizza from the oven. Drizzle 1 teaspoon extra-virgin olive oil over the top and sprinkle with 2 tablespoons freshly grated Parmesan if using. Crack fresh black pepper over to taste. Let the pizza rest 2–3 minutes, then slice and serve hot.