Creamy Cauliflower Dip
1 medium head of cauliflower (about 2 pounds), florets and stem cut into 1-inch pieces
1 garlic clove, peeled
1/4 cup olive oil, divided, plus more for serving
1 medium onion, thinly sliced
1 teaspoon ground cumin
2 teaspoons kosher salt, divided
3/4 cup plain Greek yogurt
1 teaspoon finely grated lemon zest
3 tablespoons fresh lemon juice
Coarsely chopped parsley (for serving)
Baby romaine hearts and endive leaves (for serving)
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.
Dip can be made 5 days ahead; cover and chill.