This recipe comes courtesy of Amanda Hesser and Merrill Stubbs, co-authors of "The Food52 Cookbook".
Trim and cut broccoli rabe into 1/2-inch pieces and place in a large skillet. Stir in olive oil and water; season with salt. Cover and cook over high 1 minute. Uncover and cook, stirring, until broccoli rabe is tender and water is evaporated, 4 minutes. Stir in cream and lemon juice; season with salt and pepper. Divide ricotta among crostini and top with broccoli rabe mixture and lemon zest.