Lightly spray a 23 cm (top measurement) round ovenproof pie dish with oil.
Heat rice in microwave following packet directions. Transfer to a large bowl. Cool 10 minutes. Lightly beat 1 egg and stir into rice with half the grated cheese until well combined. Press mixture evenly over base and sides of prepared pie dish. Bake in a preheated 180 °C oven (fan-forced) for 15 minutes or until firm.
Meanwhile, heat oil in a large non-stick frying pan over medium-high heat. Add onion and garlic. Cook, stirring, for 2-3 minutes, until lightly golden. Add spinach and lentils. Cook, stirring, for 3-4 minutes, until excess liquid has evaporated. Cool 10 minutes.
Whisk ricotta and remaining eggs in a large bowl until combined. Stir in spinach mixture and remaining grated cheese. Season with freshly ground pepper. Spoon mixture into rice crust. Smooth over top.
Bake in same oven for about 35 minutes or until filling is set. Meanwhile toss salad leaves and tomatoes in a bowl. Serve flan with salad.