Prepare the dough, leave it to rise, and then punch it down according to the instructions on page 172.
Preheat the oven to 500 degrees if it goes that high, or to at least 425 degrees. Put in a baking sheet to heat up.
While the dough is rising, shred the kale leaves into ¼ to 1/3-inch wide ribbons. Heat the oil in a frying pan over medium heat and add the onions. Once sizzling, decrease the heat to low and cook gently, stirring from time to time, until the onions are soft and golden, 10 to 15 minutes, adding the garlic halfway through. Stir the shredded kale into the onions and cook for a further 5 minutes, stirring often, until the leaves have wilted. Season with salt and pepper.
After punching down the risen dough, leave it to rest for a few minutes, then cut it into three pieces. Roll out one piece as thinly as you can.
Scatter a baking peel (if you have one) or another baking sheet with a little flour and place the rolled-out dough on it. Spread one-third of the kale and one-third of the onions on the dough, then top with one-third of the grated Cheddar. Trickle with a little oil.
Slide the pizza onto the hot baking sheet in the oven if formed on a peel, or, if formed on a baking sheet, simply lay the baking sheet on the hot one in the oven. Bake for 10 to 12 minutes, until the crust is crisp and golden. Repeat with the remaining dough and topping. Serve hot, cut into wedges.