Heat olive oil in a Dutch oven or a large, high-sided skillet over medium-high.
Add onion, season with 1 teaspoon salt and cook, stirring often, until softened and browned, 8 to 10 minutes.
Return to the skillet: Add garlic, cumin, coriander, Kashmiri chili powder and turmeric to the onion. Stir to combine, and toast the spices, about 30 seconds.
Add the tomatoes, bell peppers, serrano chilies, 1 teaspoon salt and 1 cup of water. Stir to combine, bring to a boil, and cook, stirring occasionally, until the onions and tomatoes have broken down, the peppers are tender and the curry has thickened, 20 to 25 minutes.
Taste, and adjust for salt if desired.
Serve with roti, pita, or crusty bread for scooping and lemon or lime wedges for squeezing over.
