Meyer

"The Meyer lemon fruit is yellow and rounder than a true lemon. The skin is fragrant and thin, coloured a deep yellow with a slight orange tint when ripe. Meyer lemon fruits have a sweeter, less acidic flavor than the more common Lisbon or Eureka grocery store lemon varieties. The pulp is a dark yellow and contains up to 10 seeds per fruit." (wikipwdia.com)

This one is in my parents' back yard :-)