Whisk ⅓ cup honey; ⅓ cup hot sauce; ½ teaspoon table salt; 1 teaspoon garlic powder; and ⅛ teaspoon cayenne, if using, in bowl until spices are dissolved. Transfer ¼ cup to microwave-safe bowl and set remainder aside for serving. Combine ½ teaspoon cornstarch and remaining 1 teaspoon water in small bowl, then stir into reserved honey mixture. Microwave until thickened, about 1½ minutes, stirring halfway through. Let cool for 5 minutes.

Adjust oven rack 6 inches from broiler element and heat broiler. Line rimmed baking sheet with aluminum foil and spray with vegetable oil spray. Dry 4 salmon fillets with paper towels then season with ½ teaspoon salt. Arrange fillets skin side down on prepared sheet, spaced 1 inch apart. Brush tops and sides of fillets with microwaved honey mixture.

Broil until centers are still translucent when checked with tip of paring knife and register 125 degrees (for medium-rare), 10 to 12 minutes, brushing salmon with remaining glaze and rotating sheet halfway through broiling.

Whisk 2 tablespoons white wine vinegar and remaining ½ teaspoon salt together in bowl. Add 1 English cucumber, halved lengthwise and sliced ¼ inch thick; ⅓ cup cilantro leaves; and 1 shallot, halved and sliced thin, and toss until evenly coated. Spoon rice onto large platter and arrange salmon on top. Garnish with extra cilantro leaves. Serve with cucumber salad and reserved sauce.