In a bowl, whisk together flour, eggs, milk, melted butter, sugar, and salt until smooth. Let the batter rest for 30 minutes.

Heat a non-stick skillet and melt a little butter. Pour a ladleful of batter, swirling to coat the pan. Cook until the edges lift, flip, and cook the other side for 1 more minute. Repeat with remaining batter.

In a saucepan, combine orange juice, zest, and sugar. Cook over medium heat until the syrup thickens slightly.

Fold the crêpes into quarters and add them to the orange syrup. Stir in the orange liqueur and carefully ignite the mixture to flambé. Allow the flames to subside.

Plate the crêpes, drizzle with syrup, and garnish with additional orange zest if desired.