Heat your oven to 180°C/Fan 160°C/Gas 4. Slice the tortillas into 8 wedges each. Arrange them on 2 baking trays. Bake for 5-10 mins till they’re golden and crisp. Be careful not to let them burn. These are your tortilla chips. Set aside.
Peel and finely chop the garlic clove. Finely chop the red chilli, flicking out the seeds and white pith if you prefer things a little milder. Roughly chop the tomatoes. Drain and rinse the black beans.
Set a pan over a medium-low heat and add 1 tbsp olive oil. Slide in the garlic, chilli, ¾ tbsp smoked paprika and a pinch of salt and pepper. Fry for 2-3 mins, stirring occasionally.
Tip in the chopped tomatoes, black beans and 3 tbsp cold water. Bring to the boil, then reduce the heat to a gentle simmer, pop a lid on and cook for 15 mins till the sauce has thickened. Zest the lemon and set aside, then cut in half and stir in half of the juice.
Turn your oven up to 200°C/Fan 180°C/Gas 6. Wipe clean 1 of the baking trays used for the tortilla chips and line with baking paper. Unwrap the feta and pat dry with kitchen paper. Pop the cheese on the baking tray and bake in the oven for 10-15 mins till slightly golden on the outside.
While the feta bakes, thinly slice the spring onions, trimming off the roots, and pop in a bowl. Halve the avocado and scoop out the stone with a spoon. Remove the peel and slice the avocado into small cubes. Stir into the onions along with a good pinch of salt and pepper, the remaining lemon juice and 1 tbsp olive oil.
Lay the tortilla chips on each plate and spoon over the black beans. Top with the avocado salsa and the baked feta. Finish your nachos with a scattering of rocket leaves, spoonfuls of crème fraîche, the lemon zest and a sprinkle of the remaining smoked paprika.