A beautiful cake for summer!
Preheat the oven to 350 degrees F. Generously butter a 9-inch springform pan.
Using an electric mixer, beat the butter in a large bowl until fluffy. Add the sugar and beat until blended. Beat in eggs 1 at a time, then the lemon juice and lemon zest. Beat in the flour until smooth. Spread the batter evenly in the prepared pan.
Arrange enough nectarine slices atop batter in concentric circles to cover completely; press lightly to adhere. For the topping, mix the cinnamon and sugar in a small bowl. Sprinkle over the cake.
Bake until the cake is golden brown and a tester inserted into the center comes out clean, 40 minutes to 1 hour. Cut around the cake to loosen; remove the pan sides.