The phrase "to remove the lid" means to reveal hidden or secret information or feelings. It can also refer to allowing someone to express themselves freely or openly. Full definition
Meanwhile cook the pasta as per directions, and while cooking, then remove the lid from the sauce, continuing to cook so the sauce can thicken a little. (glutenfreedelightfullydelicious.com)
Then remove the lid from your coconut butter, and place it in the oven until soft. (catchingseeds.com)
Remove the lid of the quinoa when most of the liquid has been absorbed by the quinoa and lightly fluff the quinoa with a fork. (strawberriesforsupper.com)