20 (8-inch) wooden or bamboo skewers, soaked in water for 30 minutes
3 cups fresh flat-leaf parsley leaves
2 garlic cloves
2 tablespoons red wine vinegar
1 teaspoon crushed red pepper flakes
1 teaspoon sugar
Salt and freshly ground black pepper
1/2 cup olive oil
1 1/2 pounds beef filet, cut into 3/4-inch cubes (about 40 cubes)
Vegetable or canola oil, for the grill
1 pint cherry tomatoes
2 or 3 tomatoes, cut into bite-sized pieces
In the bowl of a food processor, blend together the parsley, garlic, vinegar, red pepper flakes, sugar, 1 1/2 teaspoons salt, and 1/2 teaspoon black pepper, until smooth. With the machine running, gradually add the olive oil and process until incorporated. Spoon half of the sauce into a medium bowl. Spoon the remaining sauce in a small serving bowl; cover with plastic wrap and refrigerate until ready to serve.
Put the beef in the medium bowl with the parsley sauce. Toss well to coat the beef. Cover and refrigerate for at least 30 minutes and up to 3 hours.
Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Lightly oil the frill pan or the grilling rack with vegetable oil. Thread the skewers starting with a cherry tomato or a bite-sized piece of a large tomato, then a cube of beef. Repeat with another tomato and another cube of beef. Continue with the remaining skewers. Grill the skewers for 2 to 3 minutes on each side (for medium-rare) or until desired doneness. Season with salt and pepper.
To serve, arrange the beef skewers on a serving platter. Drizzle with the reserved parsley sauce or serve the sauce on the side as a condiment.