Add the Brussels sprouts to a rimmed baking sheet. Drizzle with the olive oil, honey, garlic, salt and red pepper flakes. Toss to combine. Bake for about 12 to 15 minutes, stirring once halfway through, until tender. Set aside to cool slightly.
Make the pizza:
Increase the oven temperature to 500ºF. If you have a pizza stone, place it (carefully!) in the oven to heat up.
Meanwhile, on a well-floured surface, roll out and shape the pizza dough and then transfer it to a piece of parchment that has been lightly dusted with cornmeal. Brush the dough with the olive oil. Top with 1 cup of the mozzarella. Next, add the cabbage, walnuts, roasted Brussels sprouts and finally the remaining ¼ cup of the mozzarella cheese.
Transfer to the oven (put the parchment paper with the pizza directly on the hot pizza stone; if you don’t have a pizza stone, set the parchment on a large baking sheet instead). Bake the pizza until the crust is golden brown, 10-13 minutes. Sprinkle with the lemon zest and cut into slices, then serve.