Preheat oven to 350°F. Line a baking sheet with parchment paper or lightly spray with non-stick spray.
In a medium bowl, whisk together baking soda, salt, and flour. Set aside.
In a large bowl, cream together butter and granulated sugar until smooth and creamy.
Add brown sugar, egg, and vanilla. Mix until fully combined.
Gradually mix the dry ingredients into the wet ingredients until a soft dough forms.
Place Cinnamon Toast Crunch cereal into a zip-top bag and crush into small pieces. Fold the crushed cereal into the dough.
Using a medium cookie scoop, place dough balls 2 inches apart on the prepared baking sheet.
Bake for 9–10 minutes, until edges are lightly crisp and centers no longer look wet.
Cool on the baking sheet for a few minutes before transferring to a wire rack.