Preheat the oven to 350°F
Cover the lasagna with foil
Heat for 20 to 30 minutes if refrigerated
Heat for 45 to 60 minutes if frozen
Remove the foil for the last 10 minutes
Check that the center is hot
Let it rest for a few minutes before serving
Reheat individual slices in the microwave for 1 to 2 minutes
Cover microwave-safe lasagna with a damp paper towel
Heat in short intervals until warmed through