You will need 4 pieces for this one.

The back is pretty much a standard tube top back.

The front is 3 pieces: 2 contoured bust pieces (they kind of look like sunglasses), and the bottom. It's kind of like a tube top, too, but with the boobs cut out. ;)

REMEMBER TO ADD A SEAM ALLOWANCE FOR ALL OF YOUR PIECES!

Here's a more detailed look at the "sunglass" pieces for the bust for various sizes.

You may need to adjust this a bit depending on your particular shape. And I know I already said this, but remember to add seam allowances!!

The length should be half of the bust (in this case, we have a 36" bust, so our pieces are 18" long).

If you want, you can cut 4 of these instead of 2, and line the bust (recommended for sheer or very thin fabrics).

These measurements should work for 44" busts and larger.

I find it's easiest to sew the two "sunglass" pieces together first.
After that, you want to attach it to the other front piece.

Pin the bust to the front piece a lot before sewing. The curved shape can make it kind of awkward to sew.

You can add elastic or a top band to the top, and hem the bottom or add a skirt to make it a dress.

Continue on for a variation.

After sewing the two bust pieces together, cut a piece of fabric at least twice as long.

For our example, our front bust pieces are 18" long, so we want the ruffle fabric to be at least 36" in length. I gave myself a few extra inches and came up with 40".

It should be as wide as the widest part of the two pieces sewn together, in this case, 6".

Ruffle the long piece of fabric at the top and buttom edges until it's the same length as the bust piece.

You can do this just by laying it on a table, and making the ruffles with your fingers, or you can baste the ruffle (by hand or machine).

Once you've got it how you want it, the next step will be easiest if you sew the ruffles down at the top and bottom.

Sew the bust piece onto the ruffled piece.

I like to pin the two pieces together on the wrong (back) side of the fabric first, then sew on the right (top) side of the fabric (as shown).
That way, I can see what the ruffles are doing as I sew, and nothing gets wonky.