Place the cashews in a small bowl or jar and cover with boiling water. Soak for at least 15 minutes, until the cashews have softened.
Preheat the oven to 450°F.
Combine 1 tablespoon sunflower oil and ½ teaspoon ground turmeric together in a large mixing bowl. Add the cauliflower, potatoes, and carrots to the bowl and toss until well coated.
Spread the vegetables out on a large baking sheet and transfer it to the oven. Roast, stirring occa-sionally, until the vegetables are just tender, about 15-20 minutes.
Meanwhile, drain the cashews and place them in a high-speed blender or food processor. Add the tomatoes, red onion, garlic, ginger, serrano chili, and sea salt. Puree on high speed until smooth.
Heat the remaining 3 tablespoons of oil in a large skillet over medium-high heat. Add the cumin seeds to the oil and cook until they are fragrant and start to sizzle, about 2 minutes, then add the dried chili and cook for another 30 seconds.
Pour the cashew/tomato mixture into the skillet and mix in the paprika, coriander, and remaining ½ teaspoon turmeric powder. Reduce the heat to medium and simmer, stirring occasionally, until the mixture starts to thicken and darken, about 8-10 minutes.
Stir in the roasted vegetables and frozen peas, then pour in the water. Cover the pan and simmer for 5-6 minutes until the vegetables are tender and the peas are cooked through.
Remove the pan from the heat. Sprinkle in the garam masala, add more sea salt to taste, and garnish with cilantro.