Pop-tarts can be heated in which of the following?

Pop-Tarts is a brand of toaster pastries produced and distributed by Kellogg's since 1964, consisting of a sweet filling sealed inside two layers of thin, rectangular pastry crust. Most varieties are also frosted. Although sold pre-cooked, they are designed to be warmed inside a toaster or microwave oven. They are usually sold in pairs inside Mylar (previously foil) packages and do not require refrigeration.

Source: Wikipedia