Cook pasta according to instructions on package, reserving ¼ cup of pasta water after draining. Rinse pistachio nuts in cold water and towel dry to remove excess salt. In a small skillet, melt 1 tablespoon butter and sauté pistachios for about 2 minutes. In a food processor or by hand, finely mince pistachios. Add the melted butter, garlic, oil, salt and lemon juice and mince until well blended. Transfer mixture back to skillet and over low heat, add cream and cheese. Stir continuously until all is combined, and immediately add drained pasta and mix thoroughly. For a thinner sauce, add reserved pasta water until desired consistency is reached. Top with parmesan cheese and serve immediately. Serves 4-6.