stroke gradient to transparent?

Hello,

Very new to illustrator so apologies my wording isnt perfect. I am trying to fill a shape in a way that the edge of the shape is hard, but the shape is transparent in the center. i tried blurring the stroke, outlining it and cutting it out from a copy of the shape, but it seems to rasterize the gradient, and its more transparent than i was looking for.(first image) Is there a better way to achieve this effect? (second image is intended effect, just not vector artwork)