Make your pesto: In a food processor, combine all ingredients and blend until combined. Taste and adjust accordingly.
Slice halloumi and add to a skillet. Cook on medium heat for about 5 min per side or until it gets a nice golden brown. No need to add any oil to the pan, halloumi can cook on its own.
Coat bread in olive oil and add to same pan and cook for 2-3 min per side.
Add hummus pesto to toast, followed by halloumi, sliced red onion, arugula, red pepper and red pepper flakes. Enjoy!