Bring about 2 inches of water to a boil in a large saucepan.

Add the shrimp to the boiling water, ensuring they are just covered.

Boil the shrimp for 5 minutes, then drain, reserving the liquid.

Set the cooked shrimp and reserved liquid aside.

Heat 2 tablespoons of olive oil in a saucepan.

Add the chopped onions to the saucepan.

Cook and stir the onions until they are soft.

Mix in the chopped fresh parsley, white wine, drained diced tomatoes, garlic powder (if using), and remaining olive oil.

Simmer the sauce, stirring occasionally, for about 30 minutes, or until the sauce is thickened.

Allow the shrimp to cool slightly.

Remove the legs from the shrimp by pinching them.

Pull off the shells, leaving the head and tail on.

When the sauce is thickened, stir in the reserved shrimp stock and shrimp.

Bring the mixture to a simmer and cook for about 5 minutes.

Add the cubed feta cheese and remove from the heat.

Let the dish stand until the cheese starts to melt.

Serve warm.