Place bell peppers on a parchment paper covered baking sheet. Once hot, put in oven for 60 minutes. Remove peppers from oven and place in large glass bowl. Immediately cover with plastic wrap (tightly sealed) and let sweat for at least 30 minutes.
Once peppers are cooled, remove from bowl and gently remove the skin, seeds and core.
Add pistachios to food processor and blitz until finely ground. Add roasted red peppers one piece at a time. Once fully incorporated, add remaining ingredients to food processor. Continue to blitz until everything is fully incorporated and the you have reached the desired smoothness.
Keyword basil, creamy pesto, Garlic, pesto, red bell peppers, Sauce