In a large bowl, combine the chopped kale, cherry tomatoes, cucumber, red onion, feta cheese, and sunflower seeds.
In a small bowl or jar, whisk together the olive oil, lemon juice, Dijon mustard, honey, salt, and pepper until well combined.
Drizzle the lemon vinaigrette over the salad and toss gently to coat all the ingredients evenly.
Let the salad sit for about 10 minutes to allow the flavors to meld and the kale to soften slightly.
Serve immediately or refrigerate for up to 2 hours before serving for a chilled option.