Caramelised Onion Butter Bean Bake

• 2 tbsp extra virgin olive oil
• 2 red onions, finely sliced
• 1 large zucchini, halved lengthways then finely sliced
• 2 garlic cloves, crushed
• 2 tbsp tomato paste
• 400 g tin butter beans
• 0.5 cup Greek yoghurt
• 0.5 cup milk
• 0.5 cup shredded cheese
• 2 cup curly kale, finely chopped
• 50 g feta cheese
• 2 slices sourdough bread, toasted