Mince the onion.

Combine all meat sauce ingredients in a microwave-safe container.

Cover loosely with plastic wrap and microwave at 600W for 7–8 minutes until cooked, stirring occasionally.

Heat butter in a pan over low heat, add flour, and stir until no longer powdery.

Gradually add milk while stirring to avoid clumps.

Add consomme and salt, and continue stirring until thickened.

Boil spaghetti in salted water (1 tsp salt) for 1 minute less than the package instructions, then drain.

Mix spaghetti with 2/3 of the meat sauce in a heatproof dish. Add the remaining meat sauce in the center.

Pour white sauce around the edges and top with shredded pizza cheese.