The icon is a pie in the classic sense of American pie. It appears that a crust with three slits in the top is with a round pie pan. You cannot see what is inside the pie as the filling is obscured by the crust.
This is a Pie Filled icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,700 icons, all in the same style and quality.