1. SERIOUSLY DO THIS FIRST: Cook pasta in salted water according to package directions for al dente. Before straining, reserve 1/2 cup of the cooking water.
2. Heat a large skillet or frying pan to medium-high, then sauté bacon until slightly crispy, about 5 minutes. Remove bacon and place on paper-lined plate. When cool, chop bacon into 1/2-inch pieces.
3. Get rid of all but 1 tbsp of bacon fat, then sauté diced onion for 3 minutes. Add frozen peas and sauté for another 3 minutes.
4. Meanwhile, in a medium bowl, whisk together the eggs, salt, lemon juice and zest. Temper the eggs by slowly whisking the reserved pasta water into them while still hot.
5. Add the minced garlic to the skillet. Sauté until fragrant, about 30 seconds, and turn off the heat.
6. IMMEDIATELY toss cooked pasta with the bacon, garlic and egg mixture, and stir to coat evenly in the liquid.
7. Add additional pasta water, if needed. Adjust seasoning with salt and pepper, to taste. You may cook an additional 2 minutes if the egg mixture hasn't thickened up on its own (but be careful that you don't start curdling your eggs).
8. Garnish with chives and serve immediately.