Over medium heat, add the cauliflower to a small saucepan along with 1 cup of water. 20 minutes should be enough time to properly soften the cauliflower when cooking it under cover at a simmer. Place the cooked cauliflower, along with any remaining cooking liquid, in a food processor. The pan should be cleaned.
Over medium heat, warm the oil in the pan. Shallot and garlic should be added, and they should be cooked for about 3 minutes while stirring. Lemon juice, miso, mustard, 3/4 teaspoon black pepper, cayenne, and turmeric should all be thoroughly blended before being added. Add the nutritional yeast, brown sugar, and almond milk gradually while whisking, then simply bring to a simmer. Get rid of the heat.
Cauliflower should be blended until smooth. Add the heated almond milk mixture gradually while the food processor is running and process until extremely creamy.
Add the vegan Cheddar and whisk occasionally until it melts in a big saucepan over medium heat. Add the cauliflower-almond milk combination.
In the meantime, add the elbow macaroni to the boiling water and cook as directed on the package. Retain 1 cup of the pasta water after straining.
Stir the spaghetti into the sauce after adding it. To achieve the correct consistency, stir in a little of the saved pasta boiling liquid. To taste, add salt. If using, serve hot with hot sauce on the side.