Sounds like they're going to seed already. B.Rabe is a short season, cool weather crop so you probably waited too long to transplant them. (At 8-10", they're almost fully grown.) They can handle really cold temperatures so next time, try direct-seeding them in Feb/March, or transplant them when they're much, much smaller.

For now, remove the flowers and see if you get some thicker heads forming. If not, cut them down and eat the leaves and any tender portions of the stem. Then plant again in late August/ early Sept for a fall crop.

This past season my rabe produced huge leaves, but no flowers. Any suggestions?

Hi. I'm under the impression that this is fairly normal for this type. Very, very small heads (depending on conditions), lots of greens, yellow, edible flowers. You just cook and eat the whole thing. Maybe I'm misunderstanding. I haven't grown them myself (yet) so not sure. This is, however, how I get them from the local Farmer's Market. I cook and eat whole thing and it's tasty! Sound full grown to me. Unless you have no heads at all or something....