You don’t want to heat the pasta too much as cooking the basil in the pesto will cause it to lose flavor or even change colors. To safely reheat the paste to a warmer temperature place a portion on a microwave-safe plate and reheat until just warmed through. About 1-2 minutes. For large portions, place the pasta in a covered pot over medium to low heat and slowly reheat until it’s a little warmer than room temperature.