Sadly I myself cannot claim to be Welsh, I just have the privilege of living in this lovely part of the world!
I do very often make a Welsh version of the Irish dish ‘colcannon’ - I stir in leeks instead of cabbage into buttery mashed potatoes (or sometimes leeks and cabbage!) The leek is a recognised national symbols of Wales alongside the daffodil, so its a vegetable thats easy to come by here.
If you do get to visit Cardiff again, I can heartily recommend the Riverside Food Market, held most Sunday mornings. There’s some fantastic local produce and food stalls to try, and a rather nice walk along the River Taff to enjoy too.