Pulse the diced tomatoes in a blender or food processor until completely smooth.

Heat the vegetable oil in a large Dutch oven over medium heat until it shimmers. Stir in the curry powder and garam masala and cook until fragrant, about 30 seconds—keep the spices moving to prevent burning.

Add the onions, potatoes, salt, and pepper. Increase the heat to medium-high and cook, stirring frequently, until the onions have softened and are starting to brown, about 8 to 10 minutes.

Stir in the garlic, chile, ginger, and tomato paste. Cook until the tomato paste has darkened and the aromatics are highly fragrant, about 1 minute.

Stir in the cauliflower florets, water, pureed tomatoes, and chickpeas. Bring the liquid to a boil, then reduce the heat to low, cover, and simmer until the potatoes and cauliflower are tender, about 15 minutes.

Stir in the frozen peas and coconut milk. Continue to simmer uncovered until the peas are heated through and the sauce has thickened slightly, about 2 minutes.

Remove from the heat and stir in the cilantro. Adjust the seasoning with additional salt and pepper to taste and serve hot with rice.