Prep: Preheat oven to 350°F (175°C). Line baking sheets with parchment.
Cream wet ingredients: In a large bowl, beat butter and brown sugar until light and fluffy (~3 min). Add granulated sugar; mix well. Beat in egg and vanilla.
Add dry ingredients: Whisk together flour, 1 tsp cinnamon, baking soda, and salt. Gradually mix into wet ingredients until just combined.
Chill dough (optional but recommended): 30 minutes for thicker cookies.
Roll & bake:
Scoop 1½-tbsp portions. Roll into balls.
Optional: Roll in cinnamon-sugar (1 tbsp sugar + ½ tsp cinnamon).
Place 2″ apart on sheets; flatten slightly.
Bake 10–12 minutes, until edges are set but centers look soft.
Cool on pan 5 minutes, then transfer to wire rack.
