Cut baby potatoes in half. Place in a pot, cover with 1 inch of cold water, and add salt.
Simmer for 8-12 minutes until just tender when pierced with a fork.
Meanwhile, whisk together tahini, coconut yogurt, both mustards, garlic, lemon zest, lemon juice, celery seeds, caper brine, salt, pepper, and 1 tablespoon dill.
Drain potatoes and rest for 5 minutes. Add warm potatoes to the dressing and coat well.
Fold in capers, red onions, and jalapeño (if using). Sprinkle with remaining dill and chives.
Serve warm or chill for at least 1 hour before serving.
