Cut the top sirloin into 1/4-inch strips.

Season the beef strips with salt, pepper, and flour.

Melt the butter in a large skillet or pot over medium-high heat.

Brown the meat in the butter until golden brown.

Add the chopped onion and mushrooms to the skillet.

Cook until the onions are translucent and the mushrooms have softened.

Dissolve the beef bouillon cube in 1 cup of hot water.

Pour the beef broth into the skillet with the meat and vegetables.

Reduce heat to low, cover, and simmer for 30 minutes, stirring occasionally.

While the stroganoff simmers, cook the rice or noodles according to package directions.

After 30 minutes, remove the skillet from the heat.

Gently stir in the sour cream until well combined.

Be careful not to add the sour cream when the meat mixture is too hot, as it may separate.

Serve the beef stroganoff over the cooked rice or noodles.

Enjoy!