Step 1: In a medium bowl or a large resealable plastic bag, combine the soy sauce, olive oil, Worcestershire sauce, brown sugar, Dijon mustard, garlic powder, onion powder, black pepper, and red pepper flakes (if using). Whisk or shake well until the brown sugar is dissolved and all ingredients are thoroughly mixed.
Step 2: Add your steak (about 1-1.5 lbs, e.g., flank, skirt, sirloin, ribeye) to the marinade, ensuring it is completely coated. If using a bowl, cover it tightly with plastic wrap. For best results, use a non-reactive container or a freezer-safe bag.
Step 3: Place the marinating steak in the refrigerator for a minimum of 2 hours, and up to 24 hours. The longer the marinating time, the more intense the flavor will be.
Step 4: When ready to cook, remove the steak from the refrigerator. Take the steak out of the marinade and discard the excess marinade. Pat the steak thoroughly dry with paper towels to ensure a good sear.
Step 5: Cook the steak using your preferred method until it reaches your desired internal temperature (e.g., grilling, pan-searing in a hot cast-iron skillet, or broiling). Aim for a strong sear on both sides.
Step 6: Transfer the cooked steak to a cutting board and let it rest for 5-10 minutes. This crucial step allows the juices to redistribute, ensuring a tender and juicy result.
Step 7: Slice the steak against the grain into thin strips and serve immediately with your favorite sides.