Fit the pie shell to a 10 inch tart pan and prick the bottom several times with a fork.
Melt the butter in a saucepan and add the cherries. Cook for 5 - 6 minutes, shaking the pan from time to time. Add 1/4 cup of the sugar and continue cooking the sauce thickens and caramelizes slightly. Remove from heat and pass through a sieve. (You won't need the cooking juices.)
Spread the cherries on top of the tart shell.
Beat the eggs with the other 1/4 cup of sugar and the flour. Stir in the milk and the Kirsch. Pour this mixture on top of the cherries. Bake at 400° F for 40 minutes.