Wash and dry your potatoes then dice into your desired sized cubes and set aside.
Wash and peel your carrots and cop into about 1/2 inch rounds and set aside.
Wash your celery and chop into the same sizes as your carrots and set aside.
Wedge half a lemon into quarters, then cut those quarters in half, so you have eight total pieces.
Add all those vegetables to the bottom of a cast-iron or oven safe dish, be sure to leave some room int he middle for your cauliflower. Toss in some small sprigs of thyme and 1 tbsp rosemary to your vegetables.
Prep your first glaze by adding your melted butter, garlic powder, onion powder, minced thyme, minced rosemary, sage, 1 tbsp maple syrup, 1 tbsp dijon mustard and vegetable stock. Whisk that all together and set aside.
In a small bowl add 1 tbsp of maple syrup and 1 tbsp of dijon mustard and mix until well blended. Set aside.
To prep your cauliflower, remove any leaves, and large pieces of the stem so that it can sit flat. Be sure not to remove too much so that it falls apart, but just enough so that we can see a little bit into the cauliflower in order to pour some glaze in there.
Turn your cauliflower upside down and pour about 1/4 cup of the pre-made glaze into it. Turn your cauliflower back over and place in the center of your pan. Pour your first glaze over your cauliflower, but be sure to save about 1/2 cup in order to glaze half way through baking. Be sure to add a little bit of glaze over your vegetables as well!
Pour your mustard and maple syrup mixture over your cauliflower and using your hands rub it into the cauliflower all over the top.
Bake in your pre-heated oven for about 40 minutes, remove and pour remaining glaze over, then bake again for another 30-40 minutes.
Pro Tip - If you want to make it even more mustard and maple-y add another batch of a maple-mustard mixture half way through when you glaze it the second time.