NSBezierPath * path = [NSBezierPath bezierPath];
[path setLineWidth:2];
NSPoint center = { 250,250 };
[path moveToPoint: center];
[path appendBezierPathWithArcWithCenter: center
radius: 64
startAngle: 0
endAngle: 321];
[[NSColor whiteColor] set];
[path fill];
[[NSColor grayColor] set];
[path stroke];
Have a look at cocoadevcentral