The simplest way to draw a lemon is to start with the main shape of the whole fruit. To do this sketch a rough outline of the basic form of the lemon with its rind, pedicel, apex and stem. Also draw a small cap at the bottom of the flat bumpy lemon sections that have juicy insides.
In order to make your lemon drawing more realistic it is a good idea to add some shading. To do this sketch fairly short straight lines that curve around the lemons shapes. It is good to use different shades of yellow as well as green and darker shadows for a more natural effect.
Next use a fine brush to create a stipple effect. This will give your lemon drawing more texture and help to make it look more 3D. You can also apply a bit of light orange paint to the lemons segments for added effect.
With a small blending brush and some white paint you can apply highlight strokes within the leaf and between the textured shading lines from the previous step. With a little bit of effort you can even create some soft casted shadow on the ground below your lemon drawing.
To finish off our lemon drawing we can draw a long slightly curved line from the top of the oval shaped segment we drew earlier to create the stem. We can also depict some leaves on the stem using a few simple symmetrical curved lines and of course we should erase all the auxiliary pencil marks from our finished sketch.