For the avocado salsa

1. combine all ingredients in a blender. Pulse until smooth and creamy. Add additional tablespoons of water if too thick. You want the salsa to be thin enough to slowly drizzle off a spoon. Consistency should be similar to creamy ranch dressing.

For the steak

1. Whisk marinade ingredients in a small bowl. Season steak generously with salt and pepper. Place the whole steak in a 1-gallon Ziploc bag or sealable container (do not pre-slice). Pour marinade over the steak. Remove as much air from the bag as possible, seal and refrigerate for 2-4 hours.
2. Remove steak from the fridge 30 minutes before grilling. Preheat the grill with the cover down to medium-high heat. Clean the grates well. Allow the grill to get hot before cooking the steak. Reduce heat to medium.
3. For medium steak, grill for 5-6 minutes per side over medium heat with the cover down, roughly 450°F. Add additional time as needed. Always check the temperature with a digital thermometer.
4. Remove the steak from the heat and place it on a cutting board to rest for 5-7 minutes before slicing.
5. If using flank/skirt steak, find the natural grain running lengthwise through the steak. Cut the steak into thin slices against/across the grain. This is to ensure the steak is tender and easy to bite. If you slice with or in the same direction as the grain, the meat will be much tougher to bite through. Further slice into bite-sized chunks.
6. Serve tacos with warm/toasted tortillas topped with diced white onions, fresh cilantro leaves, and a spoonful of avocado salsa. See the note below on toasting tortillas.