Creamy Cauliflower Dip

Pour water into a medium saucepan to a depth of 1/4"; add cauliflower and garlic. Cover, bring to a boil over high heat, and cook until florets are very easily pierced with a paring knife, about 10 minutes. Drain and set aside. Meanwhile, heat 2 Tbsp. oil in a large skillet over medium. Add onion, cumin, and 1 tsp. salt and cook, stirring often, until onion is translucent, about 3 minutes. Increase heat to medium-high and cook, stirring often, until onion is golden brown, about 5 minutes more. Transfer onion mixture to a blender. Add yogurt, lemon zest and juice, reserved cauliflower, and remaining 1 tsp. salt and purée until smooth. With the motor running, add 2 Tbsp. oil in a steady stream until well combined. If dip is too thick, blend in 1 Tbsp. water at a time to reach desired consistency. Let cool to room temperature. To serve, spread dip in a wide bowl or platter. Drizzle with oil and top with parsley. Serve with romaine hearts and endive leaves alongside for dipping.