Warm a generous splash of olive oil in a large skillet over medium heat. Add the onion and cook until soft and beginning to brown, about 6–8 minutes.
Stir in the garlic for 30 seconds, then add the curry powder, paprika and cumin; cook briefly until fragrant to bloom the spices.
Increase the heat to medium-high and add the ground lamb; break it up and brown thoroughly. Season with salt and black pepper to taste as it cooks.
Push the meat to one side, stir in the tomato paste and let it toast a minute, then combine everything and add a splash of water if the mixture seems too thick. Simmer gently for 5–8 minutes to meld the flavors.
While the sauce simmers, make the yogurt drizzle by whisking the Greek yogurt with a squeeze of lemon juice and a small pinch of salt until smooth and slightly runny.
Melt the butter in a separate pan, then add the cooked pasta to warm and lightly coat it in butter. Transfer the pasta into the skillet with the lamb sauce and toss to combine so every strand is coated.
Serve the pasta topped with halved cherry tomatoes, crumbled feta, a drizzle of the lemony yogurt, and a scattering of chopped parsley. Finish with an extra pinch of paprika or freshly ground black pepper if desired.
