Preheat your oven to 350°F. Place your bread on a broiler-safe ungreased, unlined baking sheet.
In a medium bowl, combine softened butter, sugar, cinnamon, and vanilla. Use a fork to stir until the mixture forms a paste that is uniform in color.
Divide the cinnamon butter mixture evenly between the pieces of bread and spread it over the slices from edge to edge, completely covering each piece.
Place baking sheet on the top or center rack of your oven (you want it in the top half of your oven, but at least 5 inches from the broiler so your bread doesn’t burn). Bake for 10 minutes or until bread is lightly crispy.
Turn the broiler on high and broil toast until cinnamon sugar is bubbling, 1 to 2 minutes. If at any time the edges of your toast begin to burn, pull them out of the oven. DO NOT walk away from your toast under the broiler and watch it closely.
Allow the toast to cool slightly, slice, and enjoy!