Preheat the oven to 400ºF and move your oven rack to a low setting, so the cauliflower will be at least 4 to 6 inches away from the top heating element. Trim the bottom of the cauliflower, slicing the core so it's flush with the bottom of the rest of the cauliflower head and will stand up evenly when placed in a pan. Carefully remove any leaves from the bottom, without cutting off the florets. Rinse the cauliflower well (I like to rinse the bottom after the leaves have been cut off, to make sure there are no tiny bugs inside) and pat well to dry.
In a small bowl, mix together 3 tablespoons of olive oil, the salt, garlic powder, lemon juice and several grinds of black pepper. Use a pastry brush to stir it together, then flip the cauliflower upside down and brush the bottom of the cauliflower head with roughly half the mixture. Shake and turn the cauliflower head to help distribute the seasoning inside.
Flip the cauliflower head back over, and brush the entire outside with the remaining olive oil mixture. Be sure to use any excess that has dripped into the pan, too. Pour 1/4 cup of water into the bottom of the pan, then place the pan in the oven and roast for 60 minutes.
When the timer goes off, remove the pan and use a knife to check the core of the cauliflower. If the cauliflower is 2 pounds or less, it might be tender already. If not, return the cauliflower to the oven to cook for 15 more minutes. If you're worried about the cauliflower getting to dark on top, you can brush those areas with additional olive oil, to help slow the browning process. If your cauliflower head is 3 pounds or more, it will probably take closer to 1 hour and 30 minutes to become tender all the way through.
When the cauliflower is tender, remove it from the oven and let it cool for 10 minutes. Season with additional salt and pepper, if desired, then slice into wedges and serve warm with your favorite side dishes. Leftover cauliflower can be stored in an airtight container in the fridge for up to 5 days.
Nutrition information is for 1 of 6 slices, and is just an estimate, not a guarantee.I don't recommend roasting cauliflower ahead of time, as it can be mushy when you reheat it later. I tend to add the leftover roasted cauliflower to other dishes, like pasta and burrito bowls. It blends in seamlessly to almost any dish with this classic seasoning.