Toast the curry powder and garam masala in a small skillet over medium-high heat. Stir constantly until the spices darken slightly and become fragrant, about 1 minute, then transfer them immediately to a small bowl so they don't burn. Pulse the tomatoes and their juice in a food processor until coarsely chopped, about 3 or 4 pulses.

Heat most of the oil in a Dutch oven over medium-high heat until shimmering. Add the onions and cook, stirring occasionally, until they are softened and deeply caramelized, about 10 minutes.

Reduce the heat to medium. Clear the center of the pot and add the remaining oil, garlic, ginger, serrano, and tomato paste. Cook, mashing the mixture into the pot, until it smells fragrant. Add the cauliflower and tempeh and stir constantly until the vegetables and protein are well coated with the aromatics.

Stir in the processed tomatoes, water, and salt, scraping up any browned bits from the bottom of the pot. Increase the heat to medium-high and bring the liquid to a simmer. Cover the pot, reduce the heat to medium, and cook until the cauliflower is tender, 10 to 15 minutes.

Stir in the peas and coconut milk and cook until heated through, about 2 minutes. Remove the pot from the heat, season with extra salt to taste, and sprinkle with cilantro. Serve hot.