For the glaze: In a small saucepan over medium heat, cook the Chianti, vinegar, and sugar for 20 to 30 minutes, or until reduced by 80-percent total volume. Hold at room temperature.
For the tuna: Heat the oil in a large saute pan over high heat. Season the steaks with salt and pepper on both sides and add to the hot pan in 2 batches. Cook for 2 to 3 minutes. Flip the steaks, reduce the heat to medium-high, and cook for an additional 2 minutes. Remove the steaks from the pan and let rest for 5 minutes. Slice the steaks on the bias, 1-inch thick. Reserve the pan for the pasta.
For the pasta: Add the tomatoes, capers, olives, garlic, basil, and parsley to the pan and cook for 2 minutes. Add the orzo and spinach and cook for an additional minute. Remove from the heat and stir in the butter to finish the sauce.
To serve: Spoon the orzo onto plates, top with tuna, Parmesan, and pancetta, and drizzle with the Chianti glaze.