Combine water, unsalted butter, and salt in a small saucepan over medium-high heat. Bring to a full boil, then immediately remove from heat once the butter has melted completely, about 3 minutes.
1 cup water, 0.25 cup unsalted butter
Add all-purpose flour all at once to the boiling mixture. Stir vigorously with a wooden spoon until the mixture forms a smooth ball and pulls away from the sides, about 1 minute. Let the dough cool for 5 minutes.
1 cup all-purpose flour
Beat in eggs one at a time, mixing until fully incorporated before adding the next. The dough will appear broken initially but will come together smooth and glossy. Transfer the dough to a piping bag fitted with a large star tip.
2 large eggs
Pipe 4-inch lengths of dough directly onto parchment paper, cutting with scissors as needed. Transfer churros to the air fryer basket spaced 1 inch apart. Lightly spray churros with vegetable oil.
vegetable oil spray
Cook churros in the air fryer at 375°F for 8 to 10 minutes, flipping them halfway at 5 minutes. Churros are done when golden brown all over with no pale spots.
Immediately toss warm churros in a mixture of granulated sugar and ground cinnamon to coat evenly while still warm for best adhesion.
0.5 cup granulated sugar, 1 tablespoon ground cinnamon
