Lightly coat 1 cup of cauliflower with olive oil and roast on 400 F for 20 minutes. Stir halfway through cooking. Set aside when ready. Lower the oven temp to 350 F.
Following the instructions for the pasta, cook until al dente (keeping it a little firm, it will cook more in the oven). Drain and add to a casserole dish.
Meanwhile, bring another medium pot of water to boil. Add the onion, potato and carrot and simmer for 10-15 minutes, until the potatoes and carrots soften.
Drain the vegetables, saving 1 cup of the water it was boiled in.
Place the boiled vegetables, 1 cup of reserved liquid, cashews, nutritional yeast, salt, garlic powder, lemon juice, apple cider vinegar and sriracha into a high speed blender. Blend on high until smooth.
Evenly distribute the roasted cauliflower, broccoli, sun dried tomatoes, and chopped red pepper on top of the pasta in the casserole dish. Pour the cheese mixture over top and stir well to combine. Top with panko bread crumbs.
Cover with foil and bake at 350 F for 20 minutes. Then remove the foil and bake for 10 more minutes.