Start by getting your tortellini cooking in boiling water while you work on the meat base. In your large skillet, brown the ground beef with the diced onions until fully cooked. Make sure to drain the grease well so the final dish isn't oily.
Lower the heat immediately and melt the butter directly into the skillet with the cooked meat removed (or pushed to the side). Sprinkle the flour over the melted butter and stir constantly for a few minutes. This cooks out the raw flour taste and creates the thickening agent.
Slowly pour in the heavy whipping cream while whisking continuously to prevent any lumps from forming. As the mixture bubbles and thickens, stir in your shredded cheese gradually. Keep stirring until you have a velvety, smooth cheese sauce.
Return the drained beef, onions, and cooked tortellini into the skillet with the sauce. Add the seasonings, drained tomatoes, and most of the bacon bits, tossing gently to coat everything. Top with the remaining bacon and it is ready to serve immediately.