Mix the butter, salt, the zest and juice of the lime together with an immersion blender to make the compound butter.

Next, preheat your grill to 350 degrees for medium direct heat. Once the grill is heated up, layer the lemon slices in a bed large enough for your 4 filets (this will fill most of the surface area of a kettle grill). Slather the filets generously with the compound butter and place the filets over the lemon slices on the grill. Grill with the lid closed (vents open) for 16-18 minutes or until an instant read thermometer like a thermapen reads 145 degrees.