In a large skillet, saute onions in butter until browned and caramelized; remove with a slotted spoon and keep warm. In the same skillet, cook beef over medium heat until no longer pink; drain. Stir in the flour, brown sugar, cumin, salt and pepper until blended. Gradually add the broth; cook for 8 minutes or until liquid is absorbed. Stir in reserved onion.
Unroll dough and separate into four rectangles. Separate each rectangle at perforation into two triangles (see Fig. 1). Pinch two 6-in. sides together to form a triangle (see Fig. 2). Repeat with remaining dough.
Place point of one triangle near the end of a greased baking sheet. Place point of second triable in center of first triangle. Repeat with remaining triangle (see Fig. 3).
Spoon beef mixture in a 1-1/2-in.-wide strip down the center; sprinkle with mozzarella cheese. Starting at one end, fold alternating points across filling. Pinch ends to seal. Sprinkle with Parmesan cheese. Bake at 375° for 15-20 minutes or until golden brown. Cool for 5-10 minutes before slicing.