The phrase "extra cayenne" means adding more spice or heat to something. It refers to sprinkling or using more of the spicy seasoning called cayenne pepper to give food a stronger and hotter flavor. Full definition
You can always adjust the recipe according to your tastes, though — like adding extra cayenne or pepper! (wellandfull.com)
I used a cayenne - flavored dark chocolate for the topping, but regular would be fine — maybe sprinkled with a bit of extra cayenne for more spicy kick. (tofufortwo.net)