I know the temptation to cut into a pie hot and fresh from the oven is almost overpowering, but resist it. If you cut into a fruit pie while it’s still hot, you’ll end up with a runny filling. The filling needs a chance to cool in order for the thickeners to work and for the pie slices to hold their shape once cut.
Let the pie cool to room temperature on a cooling rack for about an hour. You can then serve it at room temperature or reheat it in a 350 degree oven for 30 minutes if you want to serve it hot.