How do you make roue and can thicken tomato sauce with it?

1. In a saucepan, melt equal amounts of butter and all-purpose flour over medium heat.

2. Stir constantly until the mixture is smooth and bubbly and has turned a light golden brown color.

3. Remove from heat and let cool for a few minutes.

To thicken tomato sauce with roux:

1. Add the roux to the tomato sauce and stir until well combined.

2. Bring to a simmer over medium heat, stirring occasionally, until the sauce has thickened to your desired consistency.

3. Season with salt and pepper to taste.