Place bamboo skewers in a plate with water and soak for 15 minutes.
Preheat broiler to HIGH.
Line a baking sheet with foil.
In the meantime, combine prepared steak cubes, peppers and onions in a large bowl.
To the steak mixture, add cumin, chili powder, paprika, cayenne pepper, salt, pepper and oil; mix until thoroughly incorporated.
Remove skewers from water.
Thread the skewers with prepared vegetables and steak
Transfer skewers to prepared baking sheet.
Roast skewers in the oven for 5 minutes; flip over and continue to cook for 4 more minutes, or until internal temperature of the steak registers at 135˚F to 140˚F.
Remove from oven.
Garnish with cilantro and serve with guacamole, if desired.
How To Grill Steak Kabobs
Preheat grill to 425˚F.
Brush grill grates with oil.
Place kabobs on the grill; grill for 8 to 10 minutes, or until internal temperature of steak registers at 140˚F.