Prep the oven and pan: Heat the oven to 400°F (200°C). Lightly grease a 9x13-inch baking dish with a drizzle of olive oil or a cooking spray.
Season the chicken: Pat the chicken dry.
Season both sides with 1/2 teaspoon salt and the black pepper. Arrange in a single layer in the baking dish.
Wilt the spinach: In a large skillet over medium heat, warm the olive oil. Add the garlic and cook 30 seconds until fragrant.
Add the spinach with a pinch of salt and sauté 1–2 minutes until just wilted. Remove from heat and let it cool slightly. If using frozen spinach, skip this step and make sure it’s squeezed very dry.
Make the creamy mixture: In a mixing bowl, combine Greek yogurt, cream cheese, mayonnaise, Parmesan, 1/2 cup mozzarella, onion powder, remaining 1/2 teaspoon salt, and red pepper flakes if using.
Stir until smooth. Fold in chopped artichokes, the sautéed (or thawed) spinach, and lemon juice.
Top the chicken: Spoon the spinach artichoke mixture evenly over the chicken breasts, fully covering them. Sprinkle the remaining 1/2 cup mozzarella on top.
Bake: Place the dish on the center rack and bake 22–28 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
The top should be bubbling with lightly golden spots.
Rest and garnish: Let the bake rest 5 minutes so the sauce sets slightly. Sprinkle with chopped parsley and a light squeeze of lemon if you like extra brightness.
Serve: Pair with rice, buttered noodles, roasted potatoes, or a simple green salad. Spoon extra sauce from the pan over each serving.