Yes. Definitely peony! Lovely flower, but doesn't do much for most of the year! Alas! But when they flower, they make it all up!
For peony to flower, its tuber needs to be baked by hot sun. It's not ideal to have it under a big tree. It needs to be baked. If you can find the hottest place for it and make sure the tuber is right at the soil surface. If the tuber was buried too deep, the madame would sulk and will not flower! They will do well where irises, cistus are happiest.
To recap
1) Find a spot with the longest amount of sunshine hours. The hottest and brightest spot in your garden
2) Tuber needs to be level with soil or even a bit raised.
The above applies to herbaceous peonies only. You could research intersectional peony care and tree peony care.