I think your problem is more than just the top layer. The rest of the part looks pretty ragged as well. Do you want to post the settings you are using? And what machine is this on? What brand of PLA are you using?
FYI - There is a setting on the "Infill" tab called "Outline Overlap" that determines the percentage of the outline extrusion that is overlapped by the infill segments. Usually a number around 5% is more than enough to make sure the 2 sections fuse together. From looking at the picture, I still think your problem is elsewhere...
Actually the rest of the part looked really good. All the junk around the bottom was a single layer raft that I had pulled off and didnt have a chance to clean up yet. I did play with the overlap and it made a big difference. I also assumed the fillament was the right size. It actually measures 1.63 so I had not compinsated for this roll. As for the brand I didnt keep track and it is not labled. I am guessing it will get better after I calibrate for the roll.
Wow, that's almost 10% of missing plastic! 1.63 to 1.75mm is a big difference. Be sure to update your filament diameter on the "Other" tab of your FFF settings. Otherwise there will be far too little plastic coming out of the nozzle, which is probably why you're seeing those voids in the top surface.
The M2 settings included with Creator are calibrated using the MakerGear supplied filament, so if a different brand of plastic has significantly different properties, you might need to make some minor tweaks to account for it.