Heat a wide skillet over medium-high. Drizzle a little oil if your sausage looks lean. Squeeze sausage out of casings (if needed) and cook, breaking it up, until browned with crispy edges. Scoop out to a plate, leaving the fat in the pan.
Add onion and red pepper with a pinch of salt. Stir until the edges pick up color and the onion turns glossy. Add garlic for the last 30 seconds.
Stir in paprika, cumin, and harissa. Let them bloom in the fat. Smells outrageous? Good.
Pour in the tomatoes. Season with salt and pepper. Simmer until slightly thickened and jammy around the edges. Stir in the browned merguez and any juices.
Make little wells, crack in the eggs, cover, and cook until whites set and yolks stay soft. Rotate the pan once to help even cooking. If you like firmer yolks, go a minute longer—your call.
Scatter herbs and feta. Squeeze a little lemon if you're feeling fancy. Serve with crusty bread, pita, or—IMO—even garlic toast.