Beat 150 g soft butter and 60 g powdered sugar with an electric mixer for 2-3 minutes until creamy. Stir in 1 medium egg yolk until combined. In a bowl, mix 180 g flour, 2 teaspoons espresso powder, and the grated lemon peel. Add the dry mixture to the butter mixture and stir until a smooth dough forms.
Transfer the dough to a piping bag fitted with a medium-sized rosette tip. Line two baking sheets with parchment paper. Pipe rosettes onto the sheets, spacing them about 5 cm apart.
Preheat the oven to 175-200°C (350-390°F) on medium to medium-high heat. Bake the first sheet for 10 minutes until lightly golden. Cool on a wire rack. Repeat with the second sheet.