Marinate the shrimp: Pat the shrimp dry. Place in a bowl and toss with the lemon juice, curry, and salt. Set aside for 15 minutes. While the shrimp rests, measure the curry powder, cumin, chili powder, turmeric, cayenne and ¼ teaspoon salt for the curry into a small bowl and set it near the stove. Make sure your other ingredients are prepped.
Cook the shrimp: In a Dutch oven or similar wide, deep pot, heat 1 tablespoon of the oil over medium high. Add the shrimp (discard any excess marinade that has collected in the bowl). Cook on both sides, just until the shrimp are cooked through, about 3 minutes. They will go from translucent to opaque and light pink (don’t overcook!). Remove to a plate.
Add the remaining 2 tablespoons oil. Add the onion and potato. Cook until the onion is softened and turning translucent, about 5 minutes.
Stir in the garlic, ginger, and your bowl of pre-measured spices. Cook, stirring constantly, for 30 seconds. The pot will be very fragrant.
Stir in the bell peppers, tomatoes, and coconut milk. Increase the heat to bring to a simmer. Partially cover the pot, and let simmer for 15 to 20 minutes, stirring periodically to prevent sticking to the bottom of the pot, until the potatoes are tender and the curry has thickened.
Stir in the lemon juice, cilantro, and shrimp along with any juices that collected in the bowl. Taste and adjust the seasoning as desired. Enjoy warm with an extra sprinkle of cilantro with rice and naan as desired.