Whisk flour, milk, eggs, melted butter, and salt until smooth. Let batter rest 10 minutes if you can.

Heat a nonstick pan over medium. Brush with a little butter. Pour 1/4 cup batter, tilt to spread thin.

Cook 1–2 minutes until edges lift, flip, and cook 30 seconds more. Stack on a plate.

Spread 1–2 tbsp cajeta on each crepe, fold or roll, and serve warm.