Grease a 9 inch cake pan or tart tin with butter.
In a small saucepan, melt the 1/4 cup and combine with brown sugar and maple syrup. Stir over moderate heat until sugar is entirely dissolved.
Pour the saucepan into the bottom of the cake pan and arrange the peach slices on top, cut side up.
Stir together the flour, baking powder, baking soda and salt. Set aside.
In a mixing bowl, cream the remaining 6 tbsp of butter with the white sugar and grated lemon zest. Beat in eggs one at a time. Fold in flour mixture alternately with sour cream.
Spoon batter evenly over the peaches. Bake at 350 deg F (150C) for about 40 minutes, until the top is golden and a cake tester comes out clean.
Set cake pan on a rack for 5 minutes, then loosen the edges of the cake and turn out onto a serving plate. Serve warm or at room temperature, with or without whipped cream.