1If you're not using fresh lemon juice, use about 3 Tbsp. of lemon juice.
On bread: you'll need enough slices of bread to be two layers in the baking dish. Use good, crusty, country bread.
preheat oven to 350
2Peel and slice peaches in thin segments and place in medium to large bowl. Add zest of lemon and lemon juice. Add 1/2 c. sugar and toss to coat all the peaches. Do not skip the lemon juice - it doesn't really impart much of a lemony flavor, but it will keep the edges of the peaches from browning and looking unappetizing. Set aside.
3Take an 8x8 baking dish and figure out how many slices of bread you'll need to make two layers of bread. Toast that many slices. Butter both sides.
Make a layer of double-buttered toast in the bottom of the baking dish. Sprinkle with cinnamon sugar.
Make a layer of peaches on top of the toast. Use about half the peaches.
Make another layer of double-buttered toast on top of the peaches. Sprinkle with cinnamon sugar.
Make a layer of peaches on top of the toast. Pour over any juice.
4In a small bowl, combine 1/3 c. flour, 1/4 c. sugar, brown sugar, cinnamon, salt. Cut the butter into small pieces and work the mixture together with your fingers until the mixture is well combined and looks like streusel topping you'd find on a coffee cake. Put the crumb topping as the top layer.