In a large ZipLoc bag combine 2 tablespoons hoisin sauce (one of the 2-tablespoon portions), 2 tablespoons soy sauce, juice of 1/2 lime, and 1/2 teaspoon garlic powder. Add the 2 pieces of salmon to the bag, seal, remove excess air, and marinate in the refrigerator for 30 minutes.
When the salmon has about 15 minutes left to marinate, break the cauliflower into florets. Pulse the florets in a food processor on low speed until they reach a rice- or couscous-like texture.
Heat 1 tablespoon olive oil in a skillet over medium heat. Add the processed cauliflower rice, sprinkle with salt to taste, cover, and cook for about 10 minutes, stirring occasionally, until tender. Keep warm.
While the cauliflower cooks (or during the remaining marinating time), prepare the produce: spiralize, ribbon, or julienne the 1 large carrot; dice the avocado; and chop the green parts only of the 2 scallions. Set aside.
Preheat the oven broiler on high and move the oven rack to the top position. Line a baking sheet with foil.
Remove the salmon from the marinade and discard the marinade. Place the salmon pieces skin-side down on the prepared baking sheet. If desired, gently pat the tops dry with a paper towel.
Use the remaining 2 tablespoons hoisin sauce as a glaze: spread about 1 tablespoon evenly over the top of each salmon piece. Sprinkle sesame seeds to taste over the glazed salmon.
Broil the salmon on the top rack for 10–12 minutes, or until the salmon flakes easily with a fork and is cooked to your preferred doneness (time will vary with thickness). Monitor closely to avoid burning the glaze.
Assemble bowls: divide the cauliflower rice between bowls, top with carrot, diced avocado, and scallions, then place a glazed salmon piece on each bowl. Serve immediately with lime wedges and extra hoisin sauce if desired.