Step 1

Preheat oven to 450°. Coarsely grind coriander and fennel seeds in spice mill or mortar and pestle.

Step 2

Transfer spice mixture to a small skillet and add chile, garlic, and ½ cup oil. Set over medium heat and cook, shaking pan occasionally, until garlic is golden brown and chile slices have shriveled slightly, about 5 minutes. Season spiced oil lightly with salt and transfer to a small bowl.

Step 3

Cook lentils in a large saucepan of simmering salted water until tender but still firm, 20–25 minutes. Drain and transfer to a medium bowl.

Step 4

While lentils are cooking, toss broccolini and lemon on a rimmed baking sheet with remaining 3 Tbsp. olive oil; season with salt. Roast, tossing halfway, until broccolini is charred in spots and lemon is softened, 7–9 minutes.

Step 5

Pour half of the reserved spiced oil over warm lentils. Add herbs and vinegar, season with salt, and toss to coat.

Step 6

Divide lentils among bowls and top with broccolini, lemon, and feta. Spoon remaining spiced oil over.

Step 7

Do Ahead: Lentils (without herbs and vegetables) can be marinated 3 days ahead. Cover and chill.