Halloumi and Roast Grape Salad with Tahini Dressing

["Preheat your oven to 200°C (180°C fan/Gas Mark 6).","Halve the red grapes and place them on a small baking tray.","Thinly slice the red onion and add it to the baking tray with the grapes.","Drizzle the grapes and onion with 1 tablespoon of olive oil, season with salt and pepper, and sprinkle with dried oregano.","Roast for 15-20 minutes, or until the grapes are softened and slightly blistered, and the onion is tender.","While the grapes and onion are roasting, prepare the tahini dressing.","In a small bowl, whisk together the tahini, lemon juice, and minced garlic.","Gradually whisk in the remaining 3 tablespoons of olive oil and 1 teaspoon of honey until you have a smooth, pourable dressing. Add a tablespoon or two of water if it's too thick.","Season the dressing with salt and pepper to taste.","Slice the halloumi into 1cm thick pieces.","Heat a non-stick frying pan or griddle over medium-high heat.","Add the halloumi slices and cook for 2-3 minutes per side, until golden brown and slightly crispy.","In a large bowl, combine the mixed salad leaves.","Add the roasted grapes and red onion to the salad leaves.","Scatter the toasted walnuts over the salad.","Arrange the warm, pan-fried halloumi on top of the salad.","Drizzle generously with the tahini dressing just before serving."]