STEAK KEBABS WITH CHIMICHURRI

• 1 kg beef, cut into 1-inch cubes
• fresh ground pepper
• 1 1/4 tsp kosher salt
• 1 large red onion, cut into large chunks
• 18 cherry tomatoes
• 6 bamboo skewers, soaked in water for 1 hour

FOR THE CHIMICHURRI SAUCE:

• 2 packed tbsp parsley, finely chopped (no stems)
• 2 packed tbsp chopped cilantro
• 2 tbsp red onion, finely chopped
• 1 clove garlic, minced
• 2 tbsp extra virgin olive oil
• 2 tbsp apple cider vinegar
• 1 tbsp water
• 1/4 tsp kosher salt
• 1/8 tsp fresh black pepper
• 1/8 tsp crushed red pepper flakes, or more to taste