How to Make It
Preheat oven to 400°F. Combine squash, canola oil, garam masala, 1 teaspoon salt, and 1/2 teaspoon black pepper in a large bowl. Toss to coat; arrange in a single layer on 2 aluminum foil–lined baking sheets. Roast until tender, about 30 minutes.
Meanwhile, heat coconut oil in a large, high-sided skillet over medium. Add mustard seeds. When seeds begin to pop, add onion and serrano. Cook, stirring, until onion is soft and golden, about 12 minutes. Add garlic and cook, stirring often, until softened, 2 to 3 minutes. Stir in peas and tomatoes. Cook until tomatoes are jammy around edges, about 3 minutes. Stir in turmeric, then coconut milk, and season with salt and pepper. Add roasted squash and fold to coat with curry. Cover and let simmer 5 minutes before serving.