In a large mixing bowl, toss the Brussels sprouts and kale with the lemon zest and a generous pinch of sea salt. Massage and squeeze the salt and lemon into the leaves. Set aside while you make the dressing.
To make the dressing, in a pint jar or small bowl, combine the shallot, lemon juice, sea salt, and red pepper flakes. Whisk in the sesame oil, honey, and tahini. If needed, thin slightly with water until mixture is smooth.
Set a small skillet over medium heat, and shaking gently, toast the sesame seeds until they are light golden and have just started to pop. Take care not to burn the seeds – if the pan is too hot, spoon them out quickly to stop the cooking process.
Toss the salad with most of the dressing. Taste and add additional dressing and sea salt as needed. Top with sesame seeds. Serve right away or store in the fridge for up to three days.