In food processor bowl, blend together the parsley, garlic, vinegar, chili flakes, sugar, 1½ tsp salt, and ½ tsp pepper until smooth.With the machine running, gradually add the olive oil until incorporated.
Place half of the mixture in a medium bowl. Place the remaining mixture in a small serving bowl. Cover with plastic wrap and refrigerate until ready to serve.
Place the beef in the medium bowl with the parsley sauce. Toss well until the beef is coated with the mixture. Cover and refrigerate for 3 hours.
Preheat a gas or charcoal grill. Thread the skewers starting with a piece of pineapple, then a cube of beef.
Repeat with another piece of pineapple and another cube of beef. Continue with the remaining skewers.
Grill the skewers for 2 to 3 minutes each side (for medium rare) or until desired doneness.
Season with salt and pepper. To serve, arrange the kebab on a serving platter.
Drizzle with the remaining reserved parsley sauce or serve the sauce on the side as a condiment.