Fennel / Cauliflower Sauce
Warm 1 T of the oil in a medium skillet. Add the onions and sauté over medium heat until the onions start to brown, about 7 minutes. Add the curry powder and 1/4 cup of the water and cook for a few minutes, stirring occasionally, until the water has evaporated. Set aside.
Place the chickpea flour, the remaining 4 1/2 cups of water and the remaining 3 T of oil in a blender and blend until smooth. Pour into a medium pot or saucepan and cook over medium heat, stirring occasionally until the mixture reaches a boil; do not cover. Add the salt. Continue to cook, stirring constantly. When the mixture begins to thicken, turn the heat down to medium-low. The heat should be just high enough that the 'polenta' bubbles like molten lava. Continue cooking for 20 to 30 minutes, uncovered, stirring to prevent sticking, until the mixture loses its raw taste.
When the 'polenta' is ready, turn off the heat and stir in the curried onions. Pour into the oiled tart pan and spread evenly with a metal spatula. Let sit for an hour or so in the refrigerator to firm (at this point, you could refrigerate the tart for up to two days).
Preheat the oven to 350F/180C. Cut the tart into serving portions and brush each with oil. Bake for 20 minutes or until the tart is heated through and the top has formed a crust. Serve with fennel / cauliflower sauce (below).
Fennel / Cauliflower Sauce
Warm 4 t of the oil in a small saucepan. Add the chickpea flour and cook over low heat, stirring constantly, for about 5 minutes, or until the roux darkens, slightly, turning a nutty golden colour. Transfer to a small bowl to cool.
Toast the fennel seeds in a dry medium skillet until fragrant. Immediately transfer them to a mortar and pestle or a spice grinder and grind to a powder.
Trim off the stalks and any discoloured parts of the fennel bulb. Cut it in half and cut out the core. Slice it thin lengthwise; you should have about 2 cups.
Warm the remaining T of oil in a large saucepan or pot. Add the onions and sliced fennel and sauté over medium heat for 7 minutes, or until the onions start to brown. Add the ground fennel seeds and sauté for a couple of minutes more. Add the cauliflower and the water. Cover and bring to a boil, then lower the heat to a simmer. Remove 1/2 cup or so of the hot liquid and pour it into the bowl with the reserved roux. Whisk vigorously to dissolve the roux in the hot water then pour the dissolved roux back into the pot. Simmer, partially covered, stirring from time to time to prevent sticking for about 20 minutes, or until the cauliflower is soft.
Puree the mixture, using an immersion blender, or puree in small batches in a regular blender (hold a towel over the top and do not fill the blender more than half full if you are pureeing while the liquid is hot).
Return the sauce to the pot and add salt to taste. Let the sauce sit for a couple of minutes to absorb the salt, then add the lemon juice, ginger juice and cayenne. Adjust salt if necessary.
Arrange tarts on a plate and top with sauce.