Linguine with Spicy Lentils and Caramelized Onions

Fried onions and lentils, scented with Lebanese Seven-Spice Mix, make for a fantastic pasta sauce. This recipe is inspired by rishta-bil-adas (Lebanese pasta with lentils) from Arto der Haroutounian’s Vegetarian Dishes from the Middle East. In that traditional recipe, equal amounts of pasta and lentils are cooked together. The combination of pasta and lentils is less common than mujadara (rice