The first problem, you shot right into a dark background which was probably less than F/16, remember, you care capturing "reflected" light from your background. If you point your meter to the sky, the Sunny 16 rule applies, but that doesn't mean your background is reflecting at F/16, it may actually be F/11 or less.
Meters are starting points based on 18-percent gray, ever seen anyone with 18-percent gray skin color? If I use a meter, I then mentally apply the 90-percent rule to make adjustments. What is pure black is going to absorb 90-percent of the light that hits it, what is pure white will reflect 90-percent of the light that hits it. In this case, your background, with green leaves is absorbing more light.
Now, additionally, your background, when shooting outdoors, is affected by ambient light, thus your shutter-speed will control the darkness/lightness of the background--the shutter speed for your subject is the duration of the flash, the tree is affected by it in this case, but not your "far away" background.
Additionally, you probably were using an incidental light meter measuring light falling on your subject, not a reflectance light meter which measures reflected light.
Finally, if I'm going to overpower the sun with flash, I incorporate more sky in my scene (see images below). Just my two centavos. Thanks for being a part of the G1 family and community, rg sends!
Re: What am I doing wrong " over powering the sun "
Re: What am I doing wrong " over powering the sun "
Re: What am I doing wrong " over powering the sun "
Re: What am I doing wrong " over powering the sun "
Re: What am I doing wrong " over powering the sun "