Set a large soup pot on the stove over medium heat.

Add the olive oil to the pot and heat it for about 30 seconds, until it looks loose and shiny.

Add the chopped onion and 1/2 teaspoon salt to the pot. Cook for 4 to 5 minutes, stirring often, until the onion is soft and the edges are lightly golden.

Pour the vegetable broth into the pot. Raise the heat to high and bring the broth to a full boil.

While the broth heats, squeeze the lemon juice into a medium bowl and remove any seeds.

Crack the eggs into the bowl with the lemon juice.

Whisk the eggs and lemon juice together until the mixture is smooth and a little frothy.

When the broth is boiling, add the rice noodles to the pot. Stir right away so the noodles separate instead of clumping together.

Cook the noodles in the boiling broth for 3 minutes, stirring once or twice, until they bend easily but still feel a little firm in the center.

Add the frozen peas to the pot. Cook for 1 minute, until the peas are hot.

Add the baby spinach to the pot. Stir for about 1 minute, until the spinach has wilted into the broth.

Turn the heat down to low. The soup should stay very hot and steamy, but it should not boil hard.