This is the Peony dress from Colette Patterns which is an elegant bateau neck sheath dress is simple to sew. It features a fully removable cummerbund style belt which can be made in a matching or contrasting fabric, closing with a single button in back.
Version 1 has 3/4 length sleeves, a contrasting belt, and in seam pockets. Version 2 has short sleeves, a matching belt, and no pockets. Sizes 0-18.