In a large bowl, combine the vegetable oil, paprika, cumin, coriander, garlic powder, onion powder, cayenne pepper, salt, and black pepper.
Add the meat cubes and mix well to coat evenly. Cover and refrigerate for at least 2 hours or overnight for better flavor.
Preheat your grill or grill pan to medium-high heat.
Thread the marinated meat onto the soaked bamboo skewers.
Place the skewers on the grill and cook, turning occasionally, until the meat is cooked through and has a nice char, about 8-10 minutes depending on the size of the meat cubes.
In a small saucepan, heat a little oil over medium heat. Add the chopped onion and minced garlic and sauté until translucent.
Stir in the tomato paste and cook for a few minutes. Add the soy sauce and vinegar, then simmer for a few minutes until the sauce thickens slightly.
Remove the skewers from the grill and let them rest for a few minutes. Serve with the optional sauce on the side.
Enjoy your meal!