Preheat oven to 190°C (375°F). Boil noodles until al dente, drain, and set aside.
In a bowl, combine yoghurt, egg, garlic, salt, pepper, and spinach. Stir until smooth.
Heat 1 tsp olive oil in a fry pan over medium heat. Sauté onion until soft (~3–4 min), add beef and cook until browned. Stir in cumin, paprika, oregano, salt, and tomatoes; cook 5 min, then remove from heat.
In a baking dish, layer: thin yoghurt mixture → noodles → beef-tomato mixture → yoghurt-spinach filling. Repeat, ending with yoghurt on top.
Melt butter with olive oil in a small pan, add chilli flakes, swirl 30–60 sec on low, and drizzle over the lasagna.
Bake 30–35 min until golden and set. Cool 5–10 min before slicing.