Put the flour and salt into a large mixing bowl. Pour in the boiling water, stir with a spoon until shaggy, then knead for 3 to 4 minutes until a smooth dough forms; cover and let it rest for 10 minutes.
While the dough rests, slice the spring onions thinly. Halve the onion and slice it into thin half-moons, finely chop the garlic, peel and mince the ginger, dice the fresh tomatoes into small cubes, and lightly bash the cucumber with the side of a knife before cutting it into rough chunks.
Toss the torn tofu with the cornstarch, 1 tbsp soy sauce, and a little black pepper until lightly coated.
Divide the dough into 4 equal pieces. Roll each piece into a thin circle, brush lightly with a little rapeseed oil, scatter over spring onions, roll it up like a cigar, coil it into a spiral, then roll it out again into a pancake about 18 cm wide.
Heat a dry medium pan over medium heat and toast the sunflower seeds for 1 to 2 minutes until nutty; tip them into a small bowl.
In the same pan, add 1 tbsp rapeseed oil and fry the tofu over medium-high heat for 6 to 8 minutes, turning occasionally, until golden and crisp on several sides; remove to a plate.
Add another 1 tbsp rapeseed oil to the pan. Cook the sliced onion for 3 minutes until softened, then add the garlic and ginger and cook for 30 seconds.
Stir in the canned diced tomatoes, fresh tomatoes, remaining soy sauce, maple syrup, sriracha, smoked paprika, sweet paprika, and water. Simmer for 5 minutes until slightly thickened.
Return the tofu to the sauce and cook for 2 more minutes so it turns glossy and sticky.
For the cucumber side, mix the smashed cucumber with lemon zest, lemon juice, sesame oil, the toasted sunflower seeds, and a pinch of salt and pepper.
Heat a large non-stick pan over medium heat with the remaining 1 tbsp rapeseed oil. Cook the pancakes one by one for about 2 to 3 minutes per side, pressing lightly with a spatula, until golden, crisp, and flaky.
Cut each pancake into wedges. Serve the sticky tofu over or beside the pancakes, with the smashed cucumber on the side.