Butterfly the lobster tails by slicing the the top of the shell with kitchen shears all the way to the base. Pull the meat out and place it gently atop the shell. Score the top of the flesh down the middle if necessary (sometimes it separates easily on its own).
In a small bowl, whisk the melted butter with pressed garlic and lemon juice. Set aside.
Brush lobster tail with avocado or olive oil and season with salt. Place the tails on a grill preheated to 400°F meat side down. Grill lobster for about 5 minutes or until it gets nice, golden grill marks. Flip it it over and grill it for 2-3 more minutes, or until the flesh turns opaque.
Brush the lobster with the butter mixture and serve immediately!