Slice the halloumi lengthwise into 4 even-sized strips. Heat a dry skillet over a medium/high heat. Add the halloumi to the pan and cook until browned on one side – about 2-3 minutes. Turn and cook until browned on the second side. A further 2-3 minutes. The halloumi should be hot through and lightly golden on both sides.
While the halloumi is cooking, finely dice the scallions, avocado, tomato, and cucumber. Add to a small bowl. Season with a little salt and pepper and toss to combine.
Add the tahini, lime juice, and olive oil to a small bowl. Whisk together until smooth and well combined. Taste and adjust seasonings, tahini, and lime juice as desired.
Arrange the four lettuce leaves across a clean work surface. Divide the avocado salsa evenly between the four lettuce leaves. Top each salsa-filled leaf with a slice of the pan-fried halloumi.
Drizzle the lime tahini dressing over the halloumi. Divide the jalapeños between the four lettuce cups, adding more or less to personal taste. Serve immediately.