In a large cast iron skillet, begin browning the beef over medium-high heat. As it begins to cook, stir in the onion until the beef has completely browned and the onions are tender. Season to taste with Red River Ranch Original or salt and pepper. Drain any grease if needed.

Meanwhile, in a medium skillet, melt the butter over medium heat. Stir in the flour with a spatula until smooth. Slowly pour in the milk. Continue cooking until the mixture thickens to a gravy. Season with salt and pepper.

Pour the gravy mixture into the hamburger skillet and stir to combine. Continue cooking 2 to 3 minutes, stirring occasionally. Add more milk, if needed, if the mixture becomes too thick.

Evenly spoon the mixture over the slices of bread and serve immediately.