Preheat oven to 350 degrees F. Line two baking sheets with parchment paper.
Combine cinnamon toast crunch cereal and apple jacks cereal in a food processor. Pulse until finely ground into a powder. Measure 2 ⅔ cups (94 grams) and place in one bowl. Set aside remaining 1 ⅓ cups (47 grams) in another bowl.
Combine flour with cinnamon, salt, and baking soda in a medium bowl and set aside.
In the bowl of a stand mixer, cream together butter with granulated sugar and brown sugar until light and fluffy, about 3-4 minutes. Add egg and vanilla extract and beat until well combined.
Add flour mixture and mix just until combined. Add 2 ⅔ cups (94 grams) cereal powder mixture and stir just until combined.
Scoop 2 tablespoons per cookie and place them on a baking sheet. Chill cookie dough in the fridge for 30 minutes.
Remove cookies and coat each one in a generous amount of the reserved 1 ⅓ cup (47 grams) cereal powder. Place cookies on prepared baking sheet, spacing them 2 inches apart. Bake cookies for 6 minutes. Remove from oven and sprinkle any remaining cereal powder evenly on top. Return cookies to oven and bake for another 4 minutes or until golden brown. Remove from oven and let cool on baking sheet for 5 minutes. Transfer to wire rack to cool completely.