Toss the pistachios in 2 tablespoons of olive oil and season with salt. Toast in the oven until golden brown, 5 to 7 minutes. Set aside to cool
Heat 2 medium saute pans over high heat. Add 2 tablespoons olive oil to each. To one of the pans add the Concord grapes and half the tarragon. To the other pan add the Fantasy and Red Flame grapes and the remaining tarragon. Blister the skins for 2 to 3 minutes for the Concord grapes and 3 to 4 minutes for the Fantasy and Red Flame grapes. Once blistered, place the grapes on a sheet pan to cool.
Split the head of the radicchio and remove the core. Slice the head into 1/4-inch ribbons and place in a mixing bowl.
Once the grapes are cool, toss them in the bowl with the radicchio and pistachios, season with salt and black pepper, and then dress with the Zinfandel Vinaigrette and mix gently.
To serve: Place on a large platter to share family style or divide the salad among 6 to 8 plates. With a vegetable peeler, shave the Pecorino over the salad and finish with a grind of black pepper.
Pour the vinegar into a mixing bowl and then gradually whisk in the oils. Once the oils are incorporated, season with salt and pepper. To help with the final balance, squeeze in a bit of lemon juice.