My husband only likes very firm, hard nectarines. When we end up with too many softer ones (the way most people like them), I make this recipe. It's great warm or at room temperature for brunch or dessert.
Preheat oven to 350 degrees. Melt 2 tablespoons butter over medium heat. Add brown sugar and cook, stirring constantly, 2 minutes. Transfer to 9" round cake pan and spread evenly. Arrange nectarine slices over top in concentric circles in pan. If using large nectarines, you will only need 2 nectarines and will make two overlapping circles. If using smaller nectarines, you may need 3 nectarines and have more circles.
Beat butter until creamy. Add sugar and continue beating until light and fluffy. Add egg substitute or eggs and beat until blended. If using egg substitute, the mixture may look slightly curdled. Stir in milk and vanilla, blending well. Stir together dry ingredients; add to batter and mix on low speed just until blended. Batter is not very thick.
Spread batter evenly over nectarines. Bake cake until wooden pick tests clean, about 30-35 minutes. Let cool on wire rack 10 minutes, then invert onto serving platter. Cut into wedges to serve.
This is great, warm, for brunch. For dessert, I sometimes add slightly sweetened whipped cream.