Peel and devein shrimp, reserving shells and heads. Chop shrimp into bite-sized pieces.

To make shrimp stock, combine shrimp shells and heads, onion, and celery in a large pot. Squeeze lemon juice into the pot, then add lemon halves as well. Add dried basil, oregano, thyme, peppercorns, parsley, and water. Cover the pot and bring it to a boil, then reduce heat and simmer uncovered for 1 hour, skimming away any foam or impurities. Strain shrimp stock and set aside.

Heat butter in a large skillet over medium heat. Cook shrimp pieces until pink and almost cooked through, 1 to 2 minutes. Remove and set aside. Add shallots to the pan and cook until softened and translucent, about 5 minutes.

Stir in garlic, lemon zest, salt, and freshly ground pepper. Cook for 30 seconds, then add white wine. Bring to a boil and cook until white wine is reduced by half, about 5 minutes. Add shrimp stock to the pan, bring it to a boil, and simmer until reduced by half, approximately 15 minutes.

Fill a large pot with heavily salted water and bring to a rolling boil over high heat. Add ravioli and cook until they float to the top and are hot, about 3 to 4 minutes. Drain, reserving a little pasta-cooking water.

Stir diced tomatoes and cream into the shrimp sauce and heat through. Return shrimp to the pan, taste the sauce, and adjust seasoning with salt and pepper. Fold ravioli into the sauce.