Preheat the oven to 425 degrees F. Pat salmon dry with a paper towel. Trim the hard ends off of the asparagus and place both salmon and asparagus onto a sheet pan. Season with salt and pepper.
Mix together mayo, cajun seasoning, garlic powder, and honey in a small bowl to make the marinade for the salmon. Use a brush or spoon to spread the marinade all over the salmon.
Trim the hard ends off of the asparagus. Drizzle olive oil and lemon juice on top. Bake in the oven for 15-20 minutes, until the salmon is fully cooked.
While the salmon is cooking, prepare the cajun honey butter sauce. Add butter to a medium sized saucepan over medium heat. Melt the butter, then add diced garlic and cook for about 2-3 minutes, until fragrant. Add in the cajun seasoning and red pepper flakes and continue to cook for another 2 minutes.
Pour the honey, dijon mustard, and hot sauce into the saucepan and reduce the heat to low. Cook for 5-8 minutes, until slightly thickened. Add lemon juice and mayo and remove from the heat. Whisk together and set aside to cool.
Once the salmon is finished cooking, remove from the oven and add 1/2 of the glaze on top. Broil for 1-3 minutes, until golden brown.