Place garlic and butter in a small saucepan over medium-low heat, and cook until garlic is tender and golden brown (15 - 18 minutes). If you notice the garlic is turning brown, but the cloves are not softening, turn heat down and continue cooking. Pour garlic and butter into a medium bowl, and let cool.

To the bowl with the garlic and butter, add Parmesan cheese, basil, lemon zest, red pepper and pinch of kosher salt. Using a fork, mash the ingredients to combine. Season to taste with additional kosher salt. Let sit for 5 minutes before using below.

Preheat a broiler to high. Place bread on a baking sheet, and toast under the broiler until golden (about 2 minutes). Flip the slices, and broil the other side until golden (another 2 minutes). Remove the baking sheet from under the broiler, and let the bread cool slightly. Once cool enough to handle, slather the top of each slice of bread with the garlic-butter mixture, and return underneath the broiler. Cook until the cheese is golden and bubbling (about 2 minutes). Let cool for a moment then enjoy!