Heat oil in a large nonstick skillet with high sides or a Dutch oven. Add onion and cook, stirring, until translucent, about 8 minutes. Add ginger, jalapeño, garlic, and curry powder; cook, stirring, for 30 seconds. Add carrots and 2 Tbsp. water; cover and cook, stirring occasionally, until the carrots have softened, about 10 minutes (add more water if the mixture becomes dry). Add cauliflower; cover and cook, stirring occasionally, until barely tender-crisp, 5 to 10 minutes more.