Adjust oven rack to middle position and heat oven to 300 °F. Combine brown sugar, salt, and cornstarch in small bowl. Pat fish dry with paper towels and season with pepper. Sprinkle brown sugar mixture evenly over top of the fish, rubbing to distribute.
Heat oil in 12-inch ovensafe nonstick skillet over medium-high heat until just smoking. Place fish in skillet being careful not to overcrowd the pan, fish may be cooked in two batches if necessary. Cook until well browned, about 2-3 minutes. Using tongs, carefully flip fish and cook until golden, about 2 more minutes.
Remove skillet from heat and spoon glaze evenly over fillets. Transfer skillet to oven and cook until center of thickest part of fillets registers 125 °F on instant-read thermometer and is still translucent when cut into with paring knife, about 5 minutes. Transfer fillets to platter or individual plates and serve.
To plate: take about ¾ cup of rice and mound in the middle of the dinner plate. Place a glazed fish fillet on top of the rice. Arrange the pineapple salsa on top of the fish fillet, and garnish with additional basil.
Notes
Prepare the glaze before you cook the fish. If your nonstick skillet isn't ovensafe, sear the fish as directed, then transfer it to a rimmed baking sheet, glaze it, and continue as directed.