Step 1

Preheat oven to 375 degrees. Spray a 12-cup muffin pan with nonstick spray.

Step 2

Bring a large skillet sprayed with nonstick spray to medium-high heat. Cook spinach until wilted, about 2 minutes.

Step 3

Transfer spinach to a large bowl, and blot away excess moisture. Add beef, onion, egg, breadcrumbs, garlic, Italian seasoning, 1/2 tsp. salt, and pepper. Mix thoroughly. Evenly distribute mixture among the muffin cups, and smooth out the tops.

Step 4

In a medium bowl, mix ricotta with remaining 1/4 tsp. salt. Form a hole in each meatloaf, and evenly fill with ricotta mixture. Top with marinara.

Step 5

Bake until firm with lightly browned edges, about 30 minutes.

Step 6

Sprinkle with mozzarella, and bake until melted, about 5 minutes.