Allow your steak to sit on the counter for 30 minutes while you assemble the other components of the recipe.
To make the chimichurri sauce, begin by chopping the parsley, garlic and oregano as fine as you can and add them to your bowl.
Next add in your crushed red pepper, red wine vinegar, fresh lime juice and salt and pepper. Toss well.
Add a pinch of smokey paprika (optional)
Pour your grapeseed or olive oil over the mixture, toss gently and allow it to sit for the flavors to come together. You want enough oil in your small bowl to just almost cover the other ingredients, you want to see the oil in spots, that is how you know you have enough (your bowl size will determine how much oil is needed in the end).
Slice or chop your tomatoes into small pieces and place them in a bowl, add in the arugula (as much as you think you will enjoy. Set aside.
Heat the pan you will use to cook your steak on med-high heat.
Pat your steak(s) dry with a paper towel, give them a light rub (with your clean hands) of olive or grapeseed oil, season with salt and pepper and once your pan is hot (a water bead dances across the pan) place your steak(s) in. Adding additional oil in small amounts as necessary)
Get a nice crust on both sides of your steak, then check the temperature and pull your meat around 145 degrees (see notes on doneness below). Place steak(s) on a plate and allow them to rest.
Place one of your flatbreads in a pan large enough to accommodate one or two (I usually make one at a time) that has a lid you can use. All you are doing here is heating the flatbread and allowing the crust to get browned in spots. Once you flip the flatbread, sprinkle the warmed side (which is now facing up) with about 3/4 cup of mozzarella cheese (more or less - you do you). Place the lid on the pan to help the cheese melt as the other size crisps up a bit.
Slice your steak thin and into bite-sized pieces.
Give the chimichurri a stir and then take a couple spoonfulls and add it to the bowl of tomatoes and arugula, toss well with your fingers to work it in.
Pull your flatbread, top with some of the tomato/arugula mixture, top with slices of steak, spoon chimichirri over, and dig in! Repeat.