Preheat oven to 400°F (200°C). Line a baking sheet with parchment or lightly oil it.
In a small bowl, mix together the mayo, mustard, garlic, lemon juice, and paprika/chili powder.
Pat fish fillets dry and season lightly with salt & pepper.
Spread the mayo–mustard mixture evenly over all fillets.
For variety: Leave one fillet plain glazed. Sprinkle another fillet with parmesan for a little crunch. (Optional) Leave one just glazed as a control.
Bake 12–15 minutes, depending on thickness, until fish flakes easily with a fork.
Serve warm with lemon wedges on the side.