Preheat oven to 350°
In a medium bowl, combine the flour, baking powder, baking soda and salt. Set aside.
In the bowl of a standing mixer fitted with a paddle attachment, cream the butter and sugars. Add the egg and vanilla and mix until just incorporated. Add the flour mixture. When combined, add the oats and sunflower seeds.
Gently roll the cookie dough into about 12 to 18 equal-size balls. Barely flatten them and place them on a parchment-lined baking sheet.
With no more than a dozen cookies per baking sheet, bake the cookies on the bottom shelf of your oven for 8 minutes. Rotate the pan and bake for another 8 minutes.
Cool the cookies completely on the pan so that they will be crispy for the cheesecake crust. Once cool, transfer the cookies to a food processor. Pulse them into a medium crumb.