In a bowl, add the thinly sliced red onions and toss with the red wine vinegar, 1/2 tsp salt and 1/2 tsp black pepper.Toss to coat. Cover and set in the fridge to pickle.
Place the diced potatoes in a pot and fill with cold water. Bring to a boil and cook until tender.
In a small bowl, combine soy sauce, maple syrup, smoked paprika and vegetable oil. Add the crumbled tempeh and toss to coat. Heat a small pan over medium heat; add the tempeh and cook until crispy, about 5-10 minutes. Set aside to cool.
In a large bowl, add the mayo, lemon juice and zest, Dijon mustard, half the chives and combine with a pinch of salt.
Once the potatoes are cooked, drain and rinse with cold water to stop cooking and to allow the potatoes to cool. Add the cooled potatoes, pickled onions and tempeh to the large bowl with the dressing in it. Stir to combine and plate it up. Top with more chives and a squeeze of lemon!