Bring a large pot of lightly salted water to a boil over high heat. Turn broiler on high and adjust rack to upper setting in oven. Place a colander in the sink. Thoroughly rinse produce and pat dry. Cut any large cauliflower florets into bite-size pieces. Stem and mince parsley. Cut roasted red pepper into 1/2" dice. Gently crush pistachios in their bag with a pan or rolling pin.

Place a medium pan over medium heat and add 2 tsp. olive oil to hot pan. Stir in panko and let toast, stirring continuously, until crumbs are golden brown. Remove from pan and set aside. Lightly wipe out pan and set aside for mustard sauce.

Prepare a baking sheet with foil and cooking spray. Place cauliflower florets onto baking sheet. Drizzle with 2 tsp. olive oil and toss to coat evenly. Place cauliflower under broiler and cook 5-8 minutes, until cauliflower is browned, lightly charred, and tender. Remove from broiler and set aside to cool. Don't text and broil! Be sure to watch cauliflower closely so you don't end up blackening the florets.

Return pan used to toast panko to medium-high heat and add butter. Cook while stirring or swirling the pan, until butter starts to foam, turns dark tan, and gives off a nutty fragrance. Remove from heat - it will continue to cook from residual heat and turn a deep brown color. Careful, do not blacken butter. Stir in mustard, half the red pepper flakes (to taste– add more if desired), and a pinch of salt and pepper. Set aside.

Add bucatini to boiling water and cook until al dente, about 7-10 minutes. Drain bucatini in colander and return to pot. Add brown butter mustard sauce and str.

Add charred cauliflower, half the panko, half the parsley, and roasted red pepper. Stir to combine. Taste and add additional salt and pepper, if necessary. Divide between two plates and garnish with crushed pistachios, remaining parsley, remaining panko, and if you want more spice, remaining red pepper flakes.