Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper. Pat the salmon dry with paper towels and place it on the baking sheet.
In a small bowl, whisk together the mayonnaise, Dijon mustard, salt, and pepper until well combined.
In another small bowl, mix the panko breadcrumbs with the thyme, garlic powder, and paprika.
Spoon the mayonnaise mixture evenly over the salmon fillets to coat them. Then sprinkle the panko mixture on top and pat it down with the back of a spoon to make sure it sticks to the salmon.
Add the trimmed asparagus spears around the salmon, drizzle with olive oil, and season with salt and pepper. Toss gently to coat.
Bake until the salmon is flaky and the panko breadcrumbs are golden brown, about 12–15 minutes, depending on the thickness of the salmon. Serve immediately with cut lemon wedges if desired.
Video
Notes
Storage: This salmon is best served and eaten straight out of the oven; the breadcrumb topping tends to get soggy when exposed to the cold. But, if you do need to store it, keep leftovers in an airtight container in the fridge for up to 3 days.