Sirloin steak sandwiches with arugula aioli

Ingredients

• 1 tbsp paprika
• 1 tsp granulated sugar
• 1 tsp garlic powder
• 3/4 tsp salt
• 1 tsp onion powder
• 1 tsp Lawrys seasoning salt
• 1 tsp cumin
• 1/2 tsp chili powder
• 1/4 cup olive oil
• 1 kg beef sirloin roast , or grilling eye-of-round roast
• 1 cup mayonnaise
• 1 cup coarsely chopped baby arugula
• 1 tsp lemon zest
• 2 tbsp lemon juice
• 1 small shallot , minced
• 3 large red onions , cut into 1/2-in. slices
• 10 sandwich buns