Prepare a steaming basket over water in a large pot on the stove. Bring the water to a low-boil. Place the entire cauliflower head, with green leaves and stem, on the steaming basket.
Cut the lemon in half, squeeze the juice over the cauliflower, and then drop the lemon halves in the steaming basket. Cover and let steam for 5-10 minutes. If you prefer crisp veggies, steam for 5 minutes, and if you prefer softer, steam for 10 minutes.
Heat the oven to 450° F and arrange an oven rack on the upper third of the oven. Prepare a baking sheet lined with foil.
In a small bowl, whisk together the miso, ginger, maple syrup, olive oil, sesame oil, and chili-garlic sauce.
Remove the cauliflower from the steaming basket and let cool for about 5 minutes. Using clean hands, massage the miso mixture evenly around the entire cauliflower head.
Place the cauliflower on the baking sheet and let roast for 30 minutes. Check at least one time while roasting to make sure the top isn’t burning. If needed lower the oven rack.