1) Preheat the oven to 180C/Gas 4.
2) Mix the apples with the lemon juice, sugar, and cinnamon in a mixing bowl and let stand while you make the batter.
3) Lightly whisk the eggs in a large mixing bowl. Add the oil, melted butter, sugar, vanilla and water and whisk until smooth. In a separate mixing bowl combine the flour, salt, and the baking powder. Use a whisk to mix the dry ingredients together. Gradually stir the flour mixture into the wet mixture and stir just until incorporated. Do not overmix.
4) Grease and lightly flour a Bundt pan. Pour 1/4 of the batter into the pan, and then arrange a 1/3 of the apples around the top of the batter. Make 2 more layers of apples, smoothing the batter over them after each addition. Top off with the last of the batter and smooth.
5) Bake about 1 hr 10 mins, until risen, the top is nicely browned, and a sharp knife inserted in the middle of the cake comes out dry.