Preheat oven to 400°F.
Spray an 8-inch square or round nonstick baking pan with nonstick cooking spray and set aside.
Into mixing bowl sift together 2 cups flour and the granulated sugar, baking powder, baking soda, and salt; with pastry blender, or 2 knives used scissors-fashion, cut in 1/4 cup margarine until mixture resembles coarse meal.
Add eggs, buttermilk, vanilla, and lemon peel and, using electric mixer, beat just until smooth; pour batter into sprayed pan.
In small bowl combine remaining 1 tablespoon plus 1 teaspoon margarine and the brown sugar; add remaining 1/4 cup flour, the nuts, and cinnamon and mix until all ingredients are thoroughly combined and crumbly.
Sprinkle nut-crumb mixture evenly over batter and bake for 25 to 30 minutes (until cake pulls away slightly from sides of pan).
Transfer pan to wire rack and let cake cool in pan.
To serve, cut into 8 equal pieces.