Preheat oven to 350°F. Line or grease a nonstick baking sheet with cooking spray.
Bring a large pot of salted water to a boil. Add the broccoli florets to the water and cook them just until fork tender, about 5 minutes. Drain the florets and transfer them to a food processor. Pulse the broccoli a few times just until broken down down into small pieces.
Measure out 3 packed cups of the broccoli and transfer to a large bowl. Add the diced onion, breadcrumbs, egg, pepper and cheese. Mix until thoroughly combined.
Scoop balls of the mixture into your palm with a cookie scoop and mold it into a tater tot shape. Place the tots on the prepared baking sheet, spacing them about 1 inch apart.
Bake the tots for about 20 minutes then flip them once and bake them an additional 10 to 15 minutes until crisped. Remove the tots from the oven and serve with your dipping sauce of choice.