The stems of sea vegetables such as sea aster are sometimes discarded when the leaves are used in recipes. Applying heat softens as well as flavours them to be used in different ways.
Cut the tomatoes into bite size pieces. Set aside.
Peel and dice the red onion. Set aside.
Heat a frying pan to a high heat. Toss the spring onions and sea aster stems with a tablespoon of olive oil and cook until charred. Remove and set aside.
Reduce the heat to low and add another tablespoon of oil. Gently cook the radishes and asparagus until just tender. Add a tablespoon of balsamic to the pan and stir to coat vegetables. Remove from the pan.
When the vegetables are cool enough to handle, slice the spring onions, seat aster stems and asparagus into bite size pieces. If the radishes are large, halve or quarter them. Combine with the tomatoes and red onion in a large bowl.
Combine the olive oil with the balsamic vinegar and salt to taste. Dress the vegetables, stirring to make all are coated. Taste for seasoning and serve.