Before you start, preheat oven to 220°C (or 200°C fan bake). Preheat BBQ to medium-high (if using).
Pat beef dry, season with salt and toss with oil, first measure of smoked paprika and garlic salt. Prep onion.
Combine oil, vinegar, mustard and second measure of smoked paprika in a medium bowl. Whisk well and set aside.
Wrap stack of tortillas in a damp tea towel and heat in microwave for 1-2 minutes, until warm. Alternatively, wrap in foil and cook in oven or on BBQ for about 10 minutes, until warmed through.
Heat oil in a large fry-pan on medium-high heat. Cook beef for 3-4 minutes each side for medium, depending on thickness, or until cooked to your liking. Rest, covered. Alternatively, do this on the BBQ. Wipe and reserve pan.
Return pan to high heat with butter. Add onion and corn. Cook for 5-6 minutes, until tender. Season to taste with salt and pepper.
Prep carrot. Add to bowl with dressing, along with spinach and toss to combine. Season to taste with salt and pepper. Thinly slice beef.
Serve tortillas filled with salad, beef, corn, yoghurt, sweet chilli sauce and chilli flakes.