Preheat the oven to 425°F. Line a baking sheet with parchment paper (and set a wire rack on top if you have one).
Make the cucumber salad dressing: In a small bowl, whisk together the chili crisp, lime, brown sugar, sesame seeds, and salt.
Slowly whisk in the neutral oil in a thin stream until the dressing thickens and emulsifies.
Add the cucumber pieces and chopped green onions. Toss to coat, then place in the refrigerator while you cook the salmon and rice.
Cook the basmati rice using your preferred method, following package directions if needed.
Pat the salmon fillets dry. Place them on the prepared baking sheet (on the rack if using).
Spread the mayonnaise evenly over the tops of both fillets (use the full 4 tbsp total). Sprinkle with salt.
Sprinkle the brown sugar evenly over the mayonnaise (use the full 4 tbsp total) and gently spread it over the top with the back of a spoon. Sprinkle with sesame seeds.
Bake until the salmon is cooked through (about 15 minutes for thick fillets; start checking earlier if your fillets are thinner).
Broil on low for 1 minute at the end to caramelize the top (watch closely so it doesn’t burn).
Let the salmon rest for 2-3 minutes. If the salmon is skin-on, gently peel off the skin.
Serve the salmon over rice with the cucumber salad spooned on top, plus a little extra dressing.
