Finely chop the tomato and pepper. Peel and finely chop the onion. Roughly chop the cucumber.
Rinse and drain the spinach and arugula. Add to a large bowl. Toss to combine.
Add the prepared vegetables. Toss well again. Set it aside.
In a small bowl, combine the olive oil, lemon juice, mustard, erythritol, parsley, thyme, salt, and garlic powder. Mix well to combine. Optionally, prepare some more dressing and store it for later.
The mixture should be completely combined. Taste and adjust the seasoning to taste. Optionally, add a pinch of dried chives.
Crumble the goat’s cheese. Add to a bowl with vegetables and pour in the prepared dressing. Toss well to combine.
Transfer the salad to serving plates. Optionally, add some more cheese on top and garnish with sliced lemon. Serve immediately.