Trim excess fat from the steaks and cut them into 2-inch cubes. You want them bite sized, but not so small that they'll overcook.
In a large bowl, combine all the seasonings, herbs, and the brown sugar to make the cajun rub. Add the steak to the bowl. Lightly massage the rub onto the cubed steak.
Pour balsamic vinegar and olive oil on top of the cubed steak. Allow the steak to marinate at least 30 minutes before cooking.
Meanwhile, mince the garlic and slice the bell pepper.
Heat a large skillet over medium heat and melt the butter.
Remove the cubed steak from the marinade and place them in the hot skillet, along with the garlic. Cook about 3 minutes on each side, or until the outside of the steak is caramelized and crispy and the inside is medium (145 degrees F).
Remove the steak bites from the skillet and allow them to rest, while you sauté the bell peppers in the same pan. Cook peppers about 5 to 10 minutes or until fork tender.
Remove the peppers from the skillet and serve them mixed with the steak bites. Drizzle any remaining garlic butter over the steak to keep them juicy.