Place apple slices in a bowl and coat with juice from one lemon. Set aside.
Place pecan pieces in a pie tin or similar oven-proof container, and place in the oven for about 7 minutes, or until toasted. (Watch carefully to prevent burning.) Let cool.
Meanwhile place butter in a large casserole or 11x13 baking pan. Place casserole in oven until butter melts, and remove.
Spread apple slices in single layer across the melted butter in the bottom of the casserole. Sprinkle the pecan pieces, lemon zest, cinnamon, and brown sugar over the apple slices and drizzle the syrup over all.
In a medium bowl, mix together the flour, baking powder (if not using self-rising flour), sugar, and milk. Slowly pour the mixture over the apple slices and lightly spread the batter to cover the apples.
Place in the oven and bake for approximately 30 - 40 minutes until brown on the top. Remove to cool.
Whip cream until soft peaks form. Add sugar and continue to whip until peaks are stiff (but not overly stiff like butter).
Serve cobbler in bowls topped with a few tablespoons whipped cream.