Mix together flour, baking powder, and salt. Whisking constantly, pour in enough beer to form a thin batter, as for pancakes. Add olive oil and whisk again. In a large, heavy frying pan, heat about 1/2 inch of oil.

When it is hot enough for frying but not smoking, dip a slice of eggplant into batter and fry on both sides until golden brown. If it seems to be browning too quickly, reduce heat, wait a moment, then fry another slice of batter-dipped eggplant. When temperature is correct, fry dipped slices of eggplant a few at a time, drain of excess oil, and set aside to keep warm. Add peppers to oil and fry just until skin begins to blister. Drain. Then add onion and fry, tossing in oil, until pieces are heated through. Drain and set aside with eggplant to keep warm.

In a blender puree yogurt and garlic until garlic is totally dissolved.

Cut about 1/2 inch from top and bottom of eggplant. With a sharp knife, peel eggplant lengthwise in strips, making a striped pattern of peeled and unpeeled areas, each about 1 inch wide. Cut eggplant crosswise into 1/4-inch slices. Cover and set aside.

To serve, arrange slices of eggplant in a circle around the rim of a serving dish. Scatter onion and bell pepper over eggplant and drizzle yogurt-garlic sauce over all. Garnish with olives and lemon wedges. Serve at once.