Nice lighting angle that works well for this type of challenge. There are sure to be voters giving it a low score because it is a flower. Don't know if the dandelion on the right adds much to the composition. You might consider applying the rule of thirds with this type of shot where there is a lot of black space. If you were to apply that rule then put it on the right side so the flower faces toward the area with the most black space.
I'm not a flower fan, and was pleased to see not quite as many flowers in this challenge. However, your title & beautiful simplicity have convinced me that this was a great entry.
I'm wondering why you chose to shoot this as a horizontal... A piece of aluminum foil might have helped to reflect some flash and fill the shadow at the center of the flower.