In a separate pan, or the same pan as the crepes, once finished, melt the butter with the sugar on medium heat.
Cook the butter until it begins to brown slightly.
The sugar may not dissolve completely or seem separated (crystallized) - that's OK. Once the juice is added, it will all combine.
Carefully add the orange or tangerine juice and zest (it may splutter). Whisk everything together.
Bring to a simmer and cook on low to medium heat for a few minutes until slightly thickened and silky.
If you want a thicker sauce, cook it a longer. It will eventually become more of a loose syrup. This is also good!
If using alcohol, add it now. You can also flambe it, if desired.
Please see this guide on how to flambe safely: https://www.bonappetit.com/story/flambe-guide
Plating the Crepes Suzette
You can add your folded crepes directly to the pan with the Orange Butter Sauce, and serve family-style. Or, you can simply pour the sauce over individual portions of crepes.