Slow cooker beef wraps with tahini

Ingredients

• 1 large onion , thickly sliced
• 6 garlic cloves , crushed
• 1 tbsp vegetable oil
• 750 g outside round beef roast , cut in half lengthwise
• 1/2 tsp salt
• 1/2 tsp pepper
• 1/3 cup soy sauce
• 1 cup plus 1 tbsp white vinegar , divided
• 1/3 cup granulated sugar , divided
• 1 tsp hot pepper flakes
• 1/2 cup plus 2 tbsp tahini , divided
• 1 tbsp sesame oil

Pickles

• 1 1/2 tsp salt
• 2 medium carrots , peeled and cut into long matchsticks (1 cup)
• 1/2 bunch radishes , sliced (1/2 cup)
• 16 leaves of red leaf lettuce
• 2 tsp toasted sesame seeds
• 1 tbsp lemon juice
• cilantro , for garnish