Be sure to have the cream cheese and mascarpone cheese at room temperature. Do not rush the mixing, and be sure to fully cream the mixture so no lumps are present. You will need plastic wrap and tinfoil for baking this cheesecake. While covering the cheesecake completely with plastic wrap and the lack of a water bath may be a departure from the way cheesecakes are normally baked, this method will produce a wonderfully smooth, no-crack cheesecake.
In a medium bowl, combine the sugar and graham cracker crumbs and stir well. Add the melted butter and stir well to combine. Firmly press the graham cracker crumb mixture into the bottom of a 9-inch springform pan (not on the sides of the pan). Place the pan into the oven on the wire rack set on position 2. Turn the convection steam oven on by selecting the Convection Mode set to 335 °F. Set the timer for 12 minutes. After 12 minutes, remove the pan and set aside to cool. Turn the oven off and leave the door open to cool. Be sure to turn off the interior light.
For the filling: In the bowl of a stand mixer, beat the cream cheese, mascarpone cheese and sugar until smooth, occasionally scraping down the sides of the bowl with a rubber spatula. Beat in the lemon juice and vanilla. Add the eggs, 1 at a time. Continue mixing until all ingredients are well combined.
Pour the cheesecake mixture over the crust in the spring-form pan. Smooth out the top with a spoon. Cover the springform pan completely by wrapping two layers of plastic wrap over the pan and all the way to the bottom. Make sure the plastic wrap ends underneath the pan. Take the wrapped springform pan and place it on a sheet of aluminum foil. Wrap the aluminum foil up around the edges of the pan to help secure the plastic wrap (however, do not cover the top of the pan with aluminum foil). Place the pan into the oven on the wire rack set on position 2. Turn the convection steam oven on by selecting the Convection Steam Mode set to 225 °F. Bake for 1 hour and 45 minutes or until the center of the cheesecake moves slightly when the pan is gently shaken. The plastic wrap may balloon up on top while baking - this is normal. Transfer the cake to a cooling rack. Gently cut away the plastic wrap covering the top, being careful, as steam may escape. Allow the cake to cool for 1 hour. Re-cover the cheesecake with plastic wrap and refrigerate until the cheesecake is cold. Cut with a warm knife, wiping the knife off between each cut.