You need to create a rectangle with the recessed cans. 18" is too far from the cabinets to light your tops and upper cabinets. I can't tell if your sink is in the exact middle of the wall, but it looks like you would need at least three cans along each wall and then two more at the ends. These all need to be evenly spaced. You can decide what size cans when you measure it out. Put tape on the ceiling in each location to get an idea. I know it seems like a lot of light, but there is really no such thing. You can put them on a dimmer.

Thanks everyone. Should I do a staggered pattern to evenly distribute the light or have them across from each other?

Is there an exhaust fan over the range? That is probably more sensible than a ceiling fan of any sort to handle odors and smells. It should vent outside if possible. If you are putting your microwave over your range and using that as exhaust fan, you can still have it vent outside. I would think that in addition to recessed cans in ceiling, you might want a separate light over the sink (probably on its own switch). Agree with suzyq53, you can never have too much light, and can always use dimmers. I would also suggest that recessed cans be LED as well, your electricity bill will go down and you won't have to worry about replacing light bulbs very often.

I would try to have them across from each other. If you take out the fan you could have two in the middle staggered.

Thanks everyone. I will dump the fan and add more lighting. I am planning to use LED's and get a combo fan/microwave above the stove. I believe it vents outside but I will double check.

Don't forget to consider the molding on the cabinets when thinking about placement! I didn't accomodate enough space bc I did 18inches from wall (advice from designer!). Now cabs are in - and lights need to be moved bc crown molding hits the lights!