Step 1

Preheat the oven to 350 degrees F.

Step 2

In a large pot of salted, boiling water, cook the pasta shells to al dente, according to the package directions. Drain the water.

Step 3

In a cast-iron skillet over medium heat, add the olive oil.

Step 4

Add the onions, the garlic, the salt, and the pepper to the heated oil and cook, stirring often, until the onions have slightly softened.

Step 5

Add the zucchini, the corn kernels, the salt, and the pepper to the onion-garlic mixture and cook until the veggies have softened, about 5-6 minutes.

Step 6

Turn the heat off and let the veggie mixture cool slightly.

Step 7

In a large bowl, add the ricotta cheese, the egg, 1 cup of the mozzarella cheese, the parmesan cheese, and 1/3 cup of the pesto and stir to combine.

Step 8

Add the veggie mixture to the cheese mixture and stir to combine.

Step 9

Pour the marinara sauce into the same cast-iron skillet.

Step 10

Stuff each of the cooked pasta shells with 2-3 tablespoons of the filling mixture, then place them in the marinara sauce in the skillet.

Step 11

Evenly dollop the remaining pesto on top of the stuffed pasta shells and sprinkle with the remaining mozzarella cheese.

Step 12

Bake the stuffed shells until they are warm, golden, and bubbly, about 25-30 minutes.

Step 13

Transfer the cast-iron skillet from the oven and let the stuffed shells rest, about 3-5 minutes.

Step 14

Serve.