Rinse the shrimp under cold water and pat them dry with paper towels. Set aside.

In a large pan or skillet, heat the vegetable oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.

Stir in the minced garlic and grated ginger. Cook for another 1-2 minutes until fragrant, stirring constantly to prevent burning.

Add the garam masala, ground cumin, turmeric powder, chili powder, and salt. Mix well and cook for 1 minute to toast the spices.

Pour in the pureed tomatoes and bring the mixture to a simmer. Cook for about 10 minutes, allowing the flavors to meld and the sauce to thicken.

Add the shrimp to the pan, stirring them into the sauce. Cook for about 5-7 minutes, or until the shrimp turn pink and are cooked through.

If using, stir in the coconut milk for a creamier texture and let it simmer for an additional 2-3 minutes.

Remove from heat and squeeze fresh lime juice over the shrimp masala.

Garnish with fresh cilantro leaves. Serve hot with rice or naan.