Saute the base. Heat olive oil in a skillet over medium heat. Saute the onion 3-4 minutes until soft, then add half the garlic and cook 30 seconds until fragrant.
Simmer the tomato sauce. Stir in the diced tomatoes, oregano, basil, red pepper flakes, salt, and pepper. Simmer 3-4 minutes, pressing on the tomatoes to help them break down.
Transfer and add orzo. Pour the mixture into a 9x13 baking dish. Stir in the orzo, broth, and water. Cover tightly with foil.
First bake and stir. Bake at 375°F for 15 minutes, then remove and stir well — this is the step that prevents clumping.
Add feta and fresh tomatoes. Nestle the feta block into the center and scatter the fresh cherry tomatoes around it. Cover and bake another 10 minutes.
Make the crispy crumb. While that bakes, melt butter in a small skillet, add the remaining garlic and panko, and toast 3 minutes until golden.
Wilt spinach, melt cheese. Uncover, stir in the spinach until wilted, then scatter mozzarella over the top. Bake uncovered 5-8 minutes until melted and bubbly.
Finish and serve. Let rest 5 minutes. Top with the crispy garlic crumb, an optional honey drizzle, and parsley. Break the feta open with a fork right before serving.