Rinse the buckwheat under cold water. In a medium saucepan, bring 2 cups of water to a boil. Add the buckwheat and a pinch of salt, then reduce to a simmer. Cover and cook for about 12-14 minutes until tender and the water is absorbed. Remove from heat and let it sit, covered, for 5 minutes. Fluff with a fork and allow it to cool slightly. Note- I like to cook mine a bit al dente, so I do about 10 minutes.
While the buckwheat is cooking, prepare the grape tomatoes, red onion, spring onions, cucumbers, bell pepper, and Kalamata olives. Set aside until ready to use.
In a small bowl, whisk together the olive oil, Dijon mustard, lemon juice, honey (if using), garlic, rice vinegar, salt, pepper, and dried oregano until well combined.
Add the cooked and cooled buckwheat to a large salad bowl. Then add the prepared vegetables over the top along with the olives. Pour the vinaigrette over the salad and toss everything together gently.
Serve with feta cheese and a bit more fresh lemon juice. Season to taste. Enjoy this healthy and DELICIOUS salad.