Preheat the oven to 225°F (105°C) and line a baking tray with parchment paper.
Place the egg whites in a clean, grease-free mixing bowl.
Beat the egg whites on medium speed until foamy.
Gradually add the sugar, one tablespoon at a time, while continuing to beat.
Continue beating until glossy, stiff peaks form.
Add the coffee concentrate and beat briefly until fully incorporated.
Transfer the mixture to a piping bag or spoon onto the prepared baking tray in small mounds.
Bake for 1 hour.
Turn off the oven and leave the meringues inside with the door closed for another hour.
Remove from the oven and cool completely before serving.
Store in an airtight container to maintain crispness.
